1. Tutorial 11 Using and Writing Visual Basic for Applications Code

2. Objectives
Session 11.1
Learn about user-defined functions, Sub procedures, and modules
Review and modify an existing Sub procedure in an event procedure
Create a function in a standard module
Test a procedure in the Immediate window
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3. Objectives Session 11.2 Create event procedures
Compile and test functions, Sub procedures, and event procedures
Create a field validation procedure
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4. Introduction to Visual Basic for Applications
Case - Chatham Community Health Services
Creating VBA Code for the Health Database
User would like to modify the frmVisit, frmPatient, and frmVisitsAndInvoices forms to make data entry easier and to highlight important information on them
To make these modifications, you will write Visual Basic for Applications code to perform the necessary operations
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5. Introduction to Visual Basic for Applications (Cont.)
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6. Introduction to Visual Basic for Applications (Cont.)
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7. Introduction to Visual Basic for Applications (Cont.)
Visual Basic for Applications (VBA)
The programming language provided with Access and other Office programs
VBA has a common syntax and a set of common features for all Microsoft Office programs, but it also has features that are unique for each Microsoft Office program due to each program’s distinct structure and components
Coding
The process of writing instructions in a programming language
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8. Introduction to Visual Basic for Applications (Cont.)
Statement
The VBA instructions to respond to an event that occurs with an object or a form control in a database
An event could be a click on a button, or activating a textbox control.
Event-driven language
Events in the database trigger a set of instructions
Object-oriented language
Each set of instructions operates on objects in the database
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9. Introduction to Visual Basic for Applications (Cont.)
Events
A state, condition, or action that Access recognizes
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10. Introduction to Visual Basic for Applications (Cont.)
Procedures
A group of statements to perform a set of operations
User-Defined function
Performs operations, returns a value, accepts input values, and can be used in expressions
Sub procedure
Executes instructions and accepts input values, but does not return a value and cannot be used in expressions
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11. Introduction to Visual Basic for Applications (Cont.)
Modules
A group of related procedures together in an object
Declarations section
Contains statements that apply to all procedures in the module
Standard module
A database object that is stored in memory with other database objects (queries, forms, and so on) when you open the database
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12. Introduction to Visual Basic for Applications (Cont.)
Public procedure
A procedure that more than one object can use
Class module
Usually associated with a particular form or report
When you create the first event procedure for a form or report, Access automatically creates an associated form or report class module
When you add additional event procedures to the form or report, Access adds them to the class module for that form or report
Each event procedure in a class module is a local procedure, or a private procedure
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13. Using an Existing Procedure
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14. Using an Existing Procedure (Cont.)
Displaying an Event Procedure
The VBA procedure that controls the display of the message and its color for each record is in the class module for the form
Access processes the statements in the procedure when you open the form and also when the focus leaves one record and moves to another
The event called the Current event occurs when the focus shifts to the next record loaded in a form, making it the current record.
The OnCurrent property contains a reference to a macro, VBA code, or some other expression that runs when the Current event occurs
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15. Using an Existing Procedure (Cont.)
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16. Using an Existing Procedure (Cont.)
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17. Using an Existing Procedure (Cont.)
Visual Basic Editor (VBE)
The program you use to create and modify VBA code
Visual Basic Window
The program window that opens when you use VBE
Scope
Indicates where the procedure is available
If the scope is public, the procedure is available in all objects in the database
If the scope is private, the procedure is available only in the object in which it is created
Event procedures are private, by default
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18. Using an Existing Procedure (Cont.)
Control Structure
The set of VBA statements that work together as a unit
Conditional Control Structure
The evaluates an expression—the value of the Reason field and then performs one of several alternative actions based on the resulting value (or condition) of the evaluated expression
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19. Using an Existing Procedure (Cont.)
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20. Using an Existing Procedure (Cont.)
Modifying an Event Procedure
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21. Creating Functions in a Standard Module
String
The or more characters that could include alphabetic characters, numbers, spaces, and punctuation
AfterUpdate Event
Triggered when a user enters or changes a field value in a control or in a form and then changes the focus
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22. Creating Functions in a Standard Module (Cont.)
Creating a Function
Each function begins with a Function statement and ends with an End Function statement
You’ll start the function with the function name and followed by a parameter, which is the value passed to the function -- called an argument
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23. Creating Functions in a Standard Module (Cont.)
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24. Creating Functions in a Standard Module (Cont.)
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25. Testing a Procedure in the Immediate Window
Logic Error
Occurs when a procedure produces incorrect results
Immediate window
Allows you to test VBA procedures without changing any data in the database
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26. Creating an Event Procedure
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27. Creating an Event Procedure (Cont.)
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28. Creating an Event Procedure (Cont.)
Designing an Event Procedure
If Statement
Executes one of two groups of statements based on a condition, similar to common English usage
True-statement group - What happens if the condition is true
False-statement group - What happens if the condition is false
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29. Creating an Event Procedure (Cont.)
Adding an Event Procedure
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30. Creating an Event Procedure (Cont.)
Compiling Modules
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31. Creating an Event Procedure (Cont.)
Testing an Event Procedure
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32. Adding a Second Procedure to a Class Module
Designing the Field Validation Procedure
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33. Adding a Second Procedure to a Class Module (Cont.)
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34. Adding a Second Procedure to a Class Module (Cont.)
Variable
A named location in computer memory that can contain a value
Dim statement
Used to declare variables and their associated data types in a procedure
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35. Adding a Second Procedure to a Class Module (Cont.)
Adding a Second Event Procedure
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36. Adding a Second Procedure to a Class Module (Cont.)
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37. Changing the Case of a Field Value
The StrConv function converts the letters in a string to all uppercase letters or to all lowercase letters, or converts the first letter of every word in the string to uppercaseletters and all other letters to lowercase letters,
[Address] = StrConv([Address], vbProperCase)
The vbProperCase constant, is a VBA constant that specifies the conversion of the first letter in every word in a string to uppercase letters and the conversion of all other letters to lowercase letters
Other VBA constants you can use are the vbUpperCase constant, which specifies the conversion of the string to all uppercase letters, and the vbLowerCase constant, which specifies the conversion of the string to all lowercase letters
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38. Changing the Case of a Field Value (Cont.)
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39. Hiding a Control and Changing a Control’s Color
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40. Hiding a Control and Changing a Control’s Color (Cont.)
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41. Hiding a Control and Changing a Control’s Color (Cont.)
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