XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 1 Enhancing User Interaction Through Programming Chapter 7 “I like thinking big. If you’re going to be thinking anything, you might as well think big.” —Donald Trump

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 2 Chapter Introduction Visual basic for applications (VBA)  Fully customize and automate a database  Perform more complex validity  Use functions and actions not available with macros

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 3 Tools Covered in This Chapter Assignment statement Breakpoints Code window DateDiff function DateSerial function Debug DoCmd statement

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 4 Tools Covered in This Chapter (continued) If statement Immediate window Northwind sample database Variables Visual basic editor Watches window

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 5 Level 1 Objectives: Writing Visual Basic for Applications Code Design create and test a subroutine in a standard module Design create, and test an event procedure Analyze decisions using procedures Design create, and test a function in a standard module

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 6 Understanding Visual Basic for Applications Programming language for Microsoft Office programs  Including Access Common syntax and set of common features for all Microsoft Office programs Features unique for each Microsoft Office program Use programming language  Write set of instructions to direct computer to perform specific operations in specific order

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 7 Understanding Visual Basic for Applications (continued) Coding Statement Event-driven language Object-oriented language

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 8 Event-Driven Programming Event  State condition or occurrence that Access recognizes  Has associated event property  Appear in property sheet for forms reports, and controls Create group of statements using VBA code  Set event property value to name of that group of statements  Event procedure

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 9 Frequently Used Access Events

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 10 Frequently Used Access Events (continued)

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 11 Common Events for Selected Controls

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 12 Coding VBA Types of procedures  Function procedures Performs operations Returns value Accepts input values Can be used in expressions  Sub procedures Performs operations and accepts input values Does not return value Cannot be used in expressions

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 13 Coding VBA (continued) Module  Group of related procedures  Starts with declarations section  One or more procedures Basic types of modules  Standard modules Database object stored in memory Use from anywhere in database  Class modules Usually associated with particular form or report

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 14 Coding VBA (continued) Public procedure  More than one object can use Local procedure or a private procedure  Only the form or report for which class module created can use event procedure

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 15 Creating a Subroutine in a Standard Module Replace macros with VBA procedures  Some tasks cannot be performed with VBA AutoKeys AutoExec

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 16 Creating a New Standard Module Click modules tab  Click new button Begin new procedure in module  Click list arrow on insert module button  Click procedure  Type name  Select options

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 17 Creating a New Standard Module (continued) Visual Basic Editor  Create and modify VBA code Visual Basic window  Program window that opens within VBE Code window  Window to create modify and display specific VBA procedures  Can have as many code windows open as modules in database

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 18 Creating a New Standard Module (continued) Sub statement  Ends with end sub statement  Includes Scope of procedure Name of procedure Opening and closing parenthesis Option compare statement  Designates technique access uses to compare and sort text data

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 19 Creating a Subroutine Type statements in procedure between Sub and End Sub statements DoCmd statement  Executes action in procedure  Access object Method  Action that operates on specific objects or controls

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 20 Creating a Subroutine (continued) Comment  Include anywhere in VBA procedure  Describe what procedure or statement does Make it easier for programmers to identify purpose of statements  Begin comment with Word Rem (for “remark”) Or single quotation mark (')  Appear green in code window

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 21 Creating a Subroutine (continued) Line label  Statement that serves as starting point for block of statements in procedure  Begins at start of line and ends with colon Underscore character at end of line  Statement continues to next line Run procedure  Click Run Sub/Userform button Saves module  Click Save button

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 22 Creating an Event Procedure

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 23 Designing an Event Procedure Associate procedure with form’s On Current event property  Triggered when form’s Current event occurs  Occurs when focus moves to record Add event procedure  Open property sheet for form  Click On Current text box  Click list arrow  Click [event procedure]  Click Build button to right of On Current text box

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 24 Making Decisions Using the If Statement Decision-making statement  Executes group of statements based on outcome of condition

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 25 Making Decisions Using the If Statement (continued) If statement  Tests condition follows one of two paths depending on outcome of condition  General form If condition Then True-statement group [Else False-statement group] End If

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 26 Making Decisions Using the If Statement (continued) Assignment statement  Assigns value of expression to control or property  Example EstSalary.ForeColor = vbGreen ForeColor property Color constants  Predefined VBA names  Have values that represent system color value

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 27 Comparison Operators and How to Use Them in Conditions

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 28 Making Decisions Using the If Statement (continued) IsNull function returns  True value when field or control null  False when not

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 29 Testing an Event Procedure Switch to form view Navigate through records  Make sure results correct in different situations

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 30 Creating a Function Similar calculation requests  Create function to perform calculation Function  Begins with Function statement  Ends with End Function statement

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 31 Variables Named location in computer memory Can contain value Use to store and retrieve data Reference using variable name assigned to location Holds only one value at a time

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 32 Variables (continued) Naming rules  Must begin with letter  Cannot exceed 255 characters  Include letters numbers and underscore character  Cannot use space, punctuation, or special characters  Cannot be same as keywords or reserved words Each variable has data type

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 33 Common VBA Data Types

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 34 Using Functions Similar to way built-in functions used Call function  Function name followed by argument(s)  Commas separate multiple arguments DateDiff function  Calculates number of time intervals between two dates

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 35 Testing a Function in the Immediate Window When statement entered  Editor checks statement to make sure syntax correct Logic error  Occurs when procedure produces incorrect results Immediate window  Test VBA procedures without changing data in database  Enter different values to test procedure

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 36 Testing a Function in the Immediate Window (continued) Immediate window  Type keyword “print” or question mark (?)  Followed by procedure name and argument values to test in parentheses and separated by commas DateSerial function  Returns date value for specified year, month, and day

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 37 Level 1 Summary VBA  Programming language for Microsoft Office programs Create procedures in module Event-driven programming  Program statement execution triggered by events If statement  Used to make decisions Function  Returns a value

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 38 Level 2 Objectives: Using Custom Functions and Verifying Data Design create and test a custom function in an event procedure Use ElseIf and If statements Verify data using event procedures Use the Case control structure

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 39 Enhancing an Event Procedure to Use a Custom Function Add and change statements in a procedure  Open object that contains event procedure in Design view  Click Code button on toolbar  Add new procedure module or class module Click Insert on menu bar Click Procedure, Module, or Class Module  Edit existing statements Scroll code window to desired statement Make necessary changes  Press Save button on Standard toolbar

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 40 Using an ElseIf Statement in an If Statement Date function  Returns current computer system date ElseIf statement  Equivalent to Else clause followed by If statement Choice of which If statement version used  Matter of personal preference Arranging order of condition testing  Order of condition testing critical  Place conditions in order from least inclusive to most inclusive

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 41 Comparing an ElseIf Clause to an Else…if Clause

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 42 Using an ElseIf Statement in an if Statement (continued) Dim statement  Declare variables and associated data types in procedure

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 43 Verifying Data with VBA Before Update event  Occurs before changed data in control or record updated in database  Use to verify entered data

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 44 Designing the Field Validation Procedure to Verify Zip Codes Cancel As Integer  Defines Cancel as parameter with Integer data type  For some events access executes attached event procedure before performing default behavior  Can cancel default behavior in event procedure or macro  Using Cancel parameter Left function  Returns string containing specified number of characters from left side of specified string

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 45 Designing the Field Validation Procedure to Verify Zip Codes (continued) Val function  Returns numbers contained in specified string as numeric value

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 46 Using the Case Control Structure Control structure  Set of VBA statements work together as a unit Case control structure  Evaluates expression  Performs one of several alternative sets of statements  Based on resulting value (or condition) of evaluated expression  Use Case Else statement as last Case statement Include false-statement group

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 47 Using the Case Control Structure (continued) CancelEvent action  Cancels event that caused procedure or macro containing action to execute Me keyword  Refers to current object Undo  Method that clears all changes made to current record SetFocus  Moves focus to specified object or control

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 48 Testing the Field Validation Procedure to Verify Zip Codes Switch to form view to test validation procedure Using event procedure for control or form  Before Update event for each control on form  Need two or more fields as part of validation process Use form’s Before Update event  Disadvantage All changes made to record undone

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 49 Designing the Field Validation Procedure to Verify Phone Area Codes Message can suggest potential error  Must accept any phone area code entry

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 50 Level 2 Summary ElseIf statement Verify data using VBA

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 51 Level 3 Objectives: Testing and Exploring VBA Troubleshoot problems in VBA procedures Compile modules Develop sources for learning VBA Explore completed modules in the Northwind sample database

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 52 Troubleshooting VBA Procedures Syntax error  Occurs when VBA statement violates language rules for statement such as Misspelling Incorrect sequence of keywords Missing parenthesis  Detected immediately when statement completed Error message opens and explains error

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 53 Syntax Error Message

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 54 Troubleshooting VBA Procedures (continued) Compilation error  Occurs when procedures translated into form computer can understand Compilation  Process of translating modules from VBA to form computer understands

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 55 Troubleshooting VBA Procedures (continued) Prevent compilation errors at run time  Use Compile command on Debug menu  Compile as last step before saving module Execution error or run-time error  Occurs when procedure executes and stops because it tries to perform operation that is impossible to perform

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 56 Using the Debugger to Correct Errors Breakpoint  Run subroutine or function up until line on which breakpoint set  Procedure halts execution at point and displays module screen  Good way to isolate place at which procedure stops producing anticipated result

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 57 Using the Debugger to Correct Errors (continued) Use mouse pointer to get more information about procedure  Pointing to variable name displays ScreenTip with value contained in variable at point that procedure halted Execute procedure one statement at a time  Try and identify cause of error  Click Debug on menu bar Click Step Into

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 58 Using the Debugger to Correct Errors (continued) Step Into  Procedure executes next statement and stops Step Out  Executes current subroutine or function and then halts Reset button  Stops debugger so you can fix problem

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 59 Identifying Errors Using the Watches Window Watches window  Shows current value of specified variable Add Watch dialog box  Enter variable name to watch “ ” in value column  Appears for watch expression  When access not executing procedure that contains watch expression

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 60 Add Watch Dialog Box

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 61 Building Procedures Slowly to Isolate Problems Prevent problems in procedures  Build them slowly using small groups of statements  Prove them to be correct as you go

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 62 Exploring VBA Powerful but complicated language Takes time to learn Know what resources available

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 63 Using the Northwind Sample Database Very efficient to reuse code included in different modules Sample Northwind database  Installed with access  Study existing procedures  Load by clicking help on menu bar in access Point to sample databases Click Northwind sample database  Contains variety of simple and complex VBA procedures

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 64 Using Help to Learn More About Programming and VBA Access Help contains valuable information about VBA Reading individual topics gives excellent background Search results list  Sample code for situations

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 65 Visual Basic Help Table Of Contents

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 66 Level 3 Summary Errors  Syntax  Compilation  Execution or run-time Debugger  Use to find and correct errors Help  Learn more about VBA

XP Chapter 7 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach 67 Chapter Summary VBA  Programming language for Microsoft Office applications Decision structures  If  ElseIf  Case Develop subroutines Use debugger to find errors