1. Spreadsheet-Based Decision Support Systems
Chapter 14: Variables
Prof. Name
Position (123)
University Name

2. Overview 14.1 Introduction 14.2 Variable Declarations and Data Types
14.3 Variable Scope
14.4 Variables in User Interface
14.5 VBA Math Functions
14.6 Applications
14.7 Summary

3. Introduction Declaring variables of different data types in VBA.
Private and public variables.
Using variables in the Message Box and Input Box user interfaces.
Mathematical, trigonometric, and derived math functions.
Conversion and string functions.
Two detailed examples of a simple DSS application which uses basic Excel object manipulation, variables, and a simple user interface.

4. Variable Declarations and Data Types
Integer and Double
String
Boolean
Constant
Range
Worksheets
Object

5. Data Types
A data type categorizes the values that can be assigned to a variable.
There are several different data types available in VBA; we will focus on the following seven data types for now, which we feel will be used most often
Integer
Double
String
Boolean
Range
Worksheets
Object

6. Defining a Variable
To declare a variable in VBA, we use the command Dim
Dim varaible As DataType
Remember that VBA for Excel is case-sensitive.
A constant variable is a variable whose value will never change.
To declare a constant, we use Const
Const variable = value
We will also see public and private declarations later.

7. Integers and Doubles Both integers and doubles are numerical values.
Integers are non-decimal numbers ranging in value from -32,768 to 32,767.
Integers will be used for simple numerical values, counting in loops, and enumerating arrays.
Doubles have values from E308 to E-324 for negative values and from E-324 to E308 for positive values.
Doubles will be used for any data or calculations.
(there are many other numerical data types such as long and single which we will not review in detail here; more information can be found on these other data types using the Microsoft Help tool).

8. String A string is a segment of text.
This text can include upper and lower-case letters, punctuation marks, and numbers; however these numbers can not be used in calculations as they will be viewed as text.
We will use strings to name objects, label objects, and label data in spreadsheets.

9. Boolean A Boolean is a variable whose value is either True or False.
We will use Boolean variables often in logic statements, If, Then statements, and loops.

10. Range
A range is a variable which can be used with all of the properties and methods of the Range object.
We must also use the Set declaration to initialize the value of a range variable.
For example, to set MyRange equal to cell A1 we would type the following.
Set MyRange = Range(“A1”)

11. Using Ranges
We will use Ranges often to increase the efficiency of our code.
We can use ranges to define what we will call a StartCell.
We set the value of this range variable at the beginning of our code and reference this StartCell variable name throughout the remainder of the code.
We may also use Ranges to make our code more dynamic.
We can use an Input Box to capture where the user wants to start a table.
Dim text As String, StartCell As Range
text = InputBox(“Enter starting cell for table:”)
Set StartCell = Range(text)

12. Worksheets The worksheets data type defines a Worksheets object.
This variable can be assigned any of the properties or methods used with the Worksheets object.
We will use this object when creating loops and/or functions to perform repeated methods or set repeated properties to multiple worksheets.

13. Object The object variable can be used to define any object in Excel.
This can be considered a drawing object, a range, a worksheet, or any other object.
Any of the properties or methods associated with any object in Excel can be used with the object variable
Even though this is a variable with a wide range of properties and methods, its running time is slower than if a specific class of objects were defined. Therefore, if we know we want to create an object variable that will only be used with properties or methods associated with the Range object, it is better to declare a range variable instead

14. Variable Scope Private and Public Variable Declarations
Keeping Track of Variable Values

15. Variable Scope
It is important to understand the scope of each variable you declare.
You must check your code to see if a variable will be used in only one sub procedure, or function procedure, or if it will be used in several different procedures.
There are two types of variable declarations which determine the scope of each variable.
Public
Private

16. Private Variables
A Private variable is declared using the Dim statement.
This variable can be private on two levels
Procedure level = only used in the particular sub procedure in which it was declared.
Module level = used in any procedure in the module, but only in the particular module in which it was declared.

17. Procedure Level vs Module Level
Procedure level private declaration
Sub Sub1()
Dim i As Integer
.....
End Sub
Sub Sub2()
....
Module level private declaration
Dim i As Integer
Sub Sub1()
End Sub
Sub Sub2()

18. Public Variables
A Public variable on the other hand can be used in any sub procedure in any module.
To declare a public variable, we use the Public statement.
Public i As Integer
We recommend using public variables in your programs. This will prevent you from finding errors when calling different sub procedures or functions

19. Keeping Track of Variable Values
There are two main ways to keep track of variable values while running your program.
Use the Watch Window
Click on View > Watch Window from the menu
Highlight any variable from the Code Window and drag it to the Watch Window
Hold your cursor over a variable name in the Code Window to see a small display of its value

20. Variables in User Interface
Message Box
Input Box

21. Message Box and Input Box
Message Boxes allow you to print something for the user to see in a small dialog box.
Input Boxes allow you to prompt the user to enter some value in a small dialog box.

22. Message Box You can print the following with a Message Box Text
Variable values
Both using concatenation with & sign
MsgBox “This is a string of text.”
MsgBox "The height is " & h & vbCrLf & " and the width is " & w & "."

23. MsgBox Function
You can also use the MsgBox function to specify button types and response types
MsgBox (prompt, [buttons], [title], [helpfile, context])
The prompt is either the text or variable (or concatenation of both) which will be displayed in the dialog box.
The title argument allows you to enter text a title for the dialog box.
The helpfile and context arguments allow you to give the user help options.
Only the prompt argument is required, all other arguments are optional.
We usually ignore the helpfile and context arguments

24. MsgBox Function (cont’d)
The buttons argument takes a VB Constant value to determine the number and style of buttons available to the user.
vbOKOnlyDisplays an OK button only
vbOKCancelDisplays OK and Cancel buttons
vbYesNoCancelDisplays Yes, No, and Cancel buttons
vbYesNoDisplays Yes and No buttons
You can also capture the user’s response to your Message Box with a VBA variable called response.
vbOKIf response was OK
vbCancelIf response was Cancel
vbAbortIf response was Abort
vbRetryIf response was Retry
vbIgnoreIf response was Ignore
vbYesIf response was Yes
vbNoIf response was No
We will see examples of using this response value in Ch 15

25. InputBox Function
The InputBox function is always assigned to a variable.
This function takes the following general form:
InputBox (prompt, [title], [default], [xpos], [ypos], [helpfile, context])
The prompt and title arguments of the InputBox function are the same as those of the MsgBox function.
The default argument allows you enter a default value to display in the Input Box.
The xpos and ypos arguments allow you to position the Input Box relative the left and top edges of the screen.
The helpfile and context arguments are the same as those of the MsgBox function.

26. InputBox Function (cont’d)
For example, you may prompt the user to enter a number and store the user value in the variable UserNumber.
UserNumber = InputBox (prompt, [title], [default], [xpos], [ypos], [helpfile, context])

27. VBA Math Functions Typical Math Functions Trigonometric Functions
Derived Math Functions
Conversion Functions
String Functions

28. VBA Math Functions
We can use typical math functions in VBA without needing to create a formula in the spreadsheet.
There are
Typical Math Functions
Trigonometric Functions
Derived Math Functions

29. Typical Math Functions
We will describe six basic math functions
Abs
Sqr
Int
Rnd
Exp
Log

30. Abs Function
The Abs function calculates the absolute value of a variable.
This function can be used with both integer and double data types (as well as with other numerical variables).
It will return the same data type which is used in the function.
Abs(-10) = 10

31. Sqr Function The Sqr function calculates the square root of a number.
It can also be used with any numerical data type (must be greater than 0).
It will always return a double data type.
Sqr(100) = 10

32. Int Function
The Int function removes the decimal part of a double variable and returns the integer part.
The result will be an integer data type.
For positive numbers, the Int function always rounds down.
For negative numbers, the Int function will return the first negative integer less than or equal to the original variable value.
Int(5.6) = 5
Int(-4.3) = -5

33. Rnd Function The Rnd function will generate a random number.
You can either enter a seed as a parameter for the function, or leave the seed value blank.
This function will return a double data type between 0 and 1.
To create random integers in a specific range, use the formula
Int((upperbound - lowerbound + 1) * Rnd + lowerbound)

34. Exp Function
The Exp function raises the constant e to some power given in the function statement.
The value returned will be a double data type.
Exp(2) = e2 =

35. Log Function
The Log function calculates the natural log, that is the logarithm with base e, of a given number.
The result is a double data type.
You can calculate logarithms with base n for any number by dividing the natural logarithm of that number by the natural logarithm of n.
For example, to calculate the log of 15 with base 10 (Log1015), you would type.
Log(15) / Log(10) =
Log base n is actually a derived function which we will talk about later in this section. We will see examples of these functions towards the end of this chapter.

36. Trigonometric Functions
There are four basic trig functions that we will describe
Sin
Cos
Tan
Atn
These functions all take angles as a parameter, and this angle value should be entered in radians.
To convert degrees to radians, multiply degrees by pi/180
To use the variable pi, we have to define a constant
Const pi = 3.14

37. Sin, Cos, and Tan Functions
The Sin, Cos, and Tan functions take an angle and return the ratio of two sides of a right triangle.
The value returned is a double data type.
The result of the Sin and Cos functions will be between -1 and 1.
Sin(pi/4) =
Cos(pi/3) = 0.5
Tan(pi/6) =

38. Atn Function
The Atn function calculates the arctangent of a given ratio.
The result is an angle in radians, which will be a double data type.
The result of the Atn function will be between -pi/2 to pi/2 radians.
To convert radians to degrees, multiply radians by 180/pi.
Atn( ) = pi/6

39. Derived Math Functions
Using the above functions, we can derive other functions.
There is a long list of examples of derived functions in Microsoft Visual Basic Help; we will demonstrate two
Arcsin
Sec
We will use function procedures to create these and other derived math functions.

40. Arcsin Function
We can derive the arcsine or inverse sine function using the Atn and Sqr functions.
We can name this the Arcsin function.
This function would be defined as follows
Arcsin(X) = Atn(X / Sqr(-X * X + 1))

41. Sec Function We can derive the secant function using the Cos function.
We can name this function Sec.
It is defined as follows.
Sec(X) = 1 / Cos(X)
We will see an example of creating a function procedure to define a derived math function in Ch 14
Use tables in Ch 13 as references for data types and math functions

42. Conversion Functions
There are several functions in VBA that can be used to convert one data type to another.
Two main conversion functions used with numerical values are CInt and CDbl.
CInt converts a variable to an Integer data type:
CInt(variable or expression)
CDbl converts a variable to a Double data type:
CDbl(variable or expression)
The Val function also extracts a numerical value from a string. The input for this function is an expression.
Val(expression)

43. Conversion Functions (cont’d)
Any numeric expression can also be converted to a string using the CStr function. The input for this function is again any variable or expression:
CStr(variable or expression)
the CDate function converts values into the Date data type. This data type is necessary to work with dates in your code for comparisons or calculations.
CDate(variable or expression)
Two other useful conversion functions are Asc and Chr. These functions, which use the ASCII list of numbers and characters, can be used to convert letters to numbers and numbers to letters, respectively:
Asc(character): Asc(“A”) = 65
Chr(number): Chr(65) = “A”

44. String Functions There are several string functions available in VBA.
Two useful string functions are UCase and LCase, which can be used to convert a string into all upper case or all lower case, respectively.
UCase(string variable or string expression)
LCase(string variable or string expression)
To extract a segment from a string value, you can use the Mid function.
Mid(string variable or string expression, starting_position, length)
MidName = Mid(“JohnHenrySmith”, 5, 5)
Another useful string function is Len. This function determines the length of a string variable value or string expression:
Len(string variable or string expression)

45. Applications Creating and Modifying Shapes
Making Calculations and Creating a Report

46. Applications (cont’d)
We consider two applications, or extended examples, in which we implement some of the new techniques learned in this chapter.
Creating and Modifying Shapes (Example 1)
Message Boxes, Input Boxes, and some various data types
Making Calculations and Creating Reports (Example 2)
Several different functions and the range data type

47. Creating and Modifying Shapes
Let us create a program in which a user can
create either a square or a circle
label their shape
position their shape on the spreadsheet
keep track of how many squares and circles have been created
delete a square or circle

48. Figure 14.1 We begin by preparing the following spreadsheet.
We have a brief description of the program, and several buttons.
Preparing your spreadsheet before writing any code is a good way to outline what code needs to be written. It also allows you to think about what can be done in Excel to save time and space in your coding.

49. Creating a Square
To do this, we will first declare variables that can be assigned to an Input Boxes to find the desired width and height of the square.
We call these variables width and height
Both of these variables should be define as double data types
Sub CreateSquare()
Dim width As Double, height As Doulbe
width = InputBox("Please enter the width of your square:",
"Width", 50)
height = InputBox("Please enter the height of your
square:", "Height", 50)
End Sub

50. Creating a Square (cont)
Now we use the AddShape method associated with the ActiveSheet and Shapes objects to create the square.
The shape type parameter should be msoShapeRectangle
The position parameters can be anything for now
The width and height parameters will be set as our variable values
ActiveSheet.Shapes.AddShape(msoShapeRectangle, , 289.5, width, height).Select
We then simply display a Message Box which tells the user that the macro has run successfully and the square has been created.

51. Figures 14.2 and 14.3
The final procedure and output are as follows:

52. Creating a Circle
This sub procedure will be very similar to creating a square.
We only need to change the msoAutoShapeType to msoShapeOval.
However, we also decide to create a new variable, radius, to be used for both the width and height values in the AddShape method.
Sub CreateCircle()
Dim radius As Double
radius = InputBox("Please enter the radius of your circle:",
“Radius", 50)
ActiveSheet.Shapes.AddShape(msoShapeOval, ,
289.5, radius, radius).Select
MsgBox “Your circle has been created.”
End Sub

53. Figures 14.4 and 14.5
The final procedure and output are as follows:

54. Counting the Shapes
We will first need two variables (which can both be integer data types):
NumSquares
NumCircles
We first need to initialize these variables to have value 0.
We cannot perform this initialization in either the CreateSquare() or CreateCircle() sub procedures since we want to increase these values each time the macros are called.
Therefore, we can either create a new sub procedure called Main() or Initialize() and assign it to a new “Start” button, or we can use the Workbook_Open() event procedure.
For now we use the Workbook event procedure.

55. Figures 14.6
The Public declaration of NumSquares and NumCircles.

56. Workbook Event Procedure
We create a Workbook_Open() event procedure in the Workbook object of our current VBA project.
In this procedure we initialize the NumSquares and NumCircles variables to be 0.
Since we want to use these variables in the Workbook object and in our main module, we must declare them as public variables with the Public statement.
We also clear the range of cells where the shapes will most likely be created and/or positioned in this event procedure.
We assume this range is A12:K50. We specify that this range is in our first worksheet and use the Delete method.

57. Figure 14.7 and 14.8 The code is as follows:
We can now create and count objects:

58. Incrementing Variable Values
To increment a variable value in VBA, use the structure
variable = variable + 1
We create two procedures for deleting squares and circles:
Similar structure to decrement variable values

59. Label Shape
To label our shape, we first prompt the user to see what text will be used as the label.
We declare a private variable called text and assign it to an Input Box as follows
text = InputBox("Please enter label for your shape:", "Shape Label", "Square 1")
Now we use the Selection object with the Characters property and Text sub property and assign the value equal to our text variable.
Selection.Characters.Text = text

60. Figures and 14.11
The procedure and result:

61. Position Shape
To position a shape, instead of asking the user to provide two numerical values for the left and top arguments of the AddShape method, we will cut and paste the selected object to a specified range.
We first declare a private variable called position to capture the range name where the user wants to move the selected object.
We then use a range variable called place to use this range value in our Paste method.

62. Position Shape (cont)
The variable declarations, InputBox function, and range assignment are written as follows
Dim position As String, place As Range
position = InputBox("Please enter cell name where you would like to position your shape (below A12):", "Position", "A12")
Set place = Range(position)
We now use the Cut method on the Selection object, and then use the ActiveSheet object and Paste method to paste the object to the desired range.
We specify this range with the Destination argument as shown below.
ActiveSheet.Paste Destination:=place

63. Figures and 14.13
Positioning the shape in cell A12.

64. Making Calculations and Creating a Report
We will create a program which can make various calculations and create reports.
The user can generate a random numbers in a specified interval and calculate its
absolute value
Integer value
square root
exponential power
natural logarithm
The user can also provide an angle to calculate its
Sine
Cosine
Tangent
We also provide a “Clear All” button to clear current reports.

65. Figure 14.14
Our spreadsheet is prepared with the appropriate buttons and table headings.
We only need three sub procedures for this program.
CalcRandNum(), CalcAngles(), and ClearAll()
We will only calculate one random number and one angle at a time for now
we will learn loop structures in Chapter 15 to expand this ability

66. Random Number Calculations
We will first ask the user to specify an interval in which they want the random number to be generated.
We will use two variables and the InputBox function to achieve this.
We declare these variables privately in the CalcRandNum() sub procedure and name them low and upp.
low = InputBox("Please enter the lower bound of the interval in which you would like to generate a random number: ", "Lower Bound", -10)
upp = InputBox("Please enter the upper bound of the interval in which you would like to generate a random number: ", "Upper Bound", 10)

67. Rand Num Calc (cont)
We now use the following function to generate a random number in this interval
x = (upp - low + 1) * Rnd() + low
We will define this x variable publicly as we will use it to perform calculations in our CalcAngles() sub procedure as well.

68. Rand Num Calc (cont)
We can insert this result into the first column of our random number calculation table.
Since we will be inserting all other random number calculations into the same table, we will use a range variable, similar to the StartCell example, for this table and use it to reference all report values.
We define this range variable publicly as we will use it in the ClearAll() procedure as well.
We name this variable RandStart and declare it as follows.
Public RandStart As Range

69. Rand Num Calc (cont)
Now we should set this variable to a particular range in the worksheet. We do this in the CalcRandNum() sub procedure by typing.
Set RandStart = Worksheets(“Example 2”).Range(“A14”)
We can now use this variable as a Range object and apply the Offset method to insert calculation results into our table. We insert the first value, the random number generated in the specified interval, into the first column.
RandStart.Offset(1, 0).Value = x

70. Figures and 14.16
We can now use the Value property of our range variable to insert all other calculations directly.
Notice that the Sqr and Log functions are used with the Abs function to ensure that no errors are created

71. Angle Calculation
For the CalcAngles() sub procedure we will begin by asking the user to enter an angle in degrees.
We do this using the InputBox function again with the prompt, title, and default value defined as shown below.
x = InputBox("Enter an angle value in degrees:", "Angle value", 45)
Notice we used the same x value as before, which was declared as a public variable.

72. Angle Calc (cont)
We now need to convert this value into radians before using any trigonometric calculations.
To do this, we will first need to declare the constant pi.
Const pi = 3.14
We can now use the following function to make the angle conversion.
x = x * pi / 180

73. Angle Calc (cont)
We will use another range variable in this procedure to insert calculation values into the angle calculation table.
We also define this variable publicly so that we can use it again in the ClearAll() procedure.
We name this variable AngleStart and declare it as follows.
Public AngleStart As Range

74. Figures and 14.18
We can now use the Offset method again to insert the original degree value of the angle, the converted radian value of the angle, and the Sin, Cos, and Tan calculation results into the report.

75. Clear All Procedure
The last procedure to write is the ClearAll() sub procedure.
This procedure will simply clear the values in both tables.
We will use the ClearContents method so as to keep the borders and other formatting of our table.
We will only clear the second row of both tables.
To do this, we will use the RandStart and AngleStart variables to define the ranges we want to clear.

76. Clear All (cont)
To clear the second row of the random number calculation table.
Range(RandStart.Offset(1, 0), RandStart.Offset (1, 5)).ClearContents
To clear the second row of the angle calculation table.
Range(AngleStart.Offset(1, 0), AngleStart.Offset (1, 4)).ClearContents

77. Summary
To declare a variable in VBA, use the command Dim. It is important to remember that VBA for Excel is case-sensitive.
There are several data types available for variables in VBA, including integer, double, string, Booleans, range, worksheet, and object.
There are two types of variable declarations: Public and Private.
Message Boxes and Input Boxes allow us to communicate with the user using VBA code. A Message Box prints information to a small dialog box, and an Input Box prompts the user to enter information into a small dialog box.
There are several math functions in VBA that can be used with variables or values. There are a few trigonometric functions in VBA that you can use with variables or values. You can also derive other functions using the pre-defined VBA functions. There are also several conversion and string functions in VBA.

78. Additional Links (place links here) Projectile
Simple forms with basic Excel manipulation
Birthday Simulation
Simple simulation with statistical analysis
Portfolio Management and Optimization
Using the Solver