Exploring Microsoft Access

Chapter 8Creating More Powerful

Applications:Introduction to VBA

ByRobert T. GrauerMaryann Barber

Exploring Microsoft Office - Microsoft Access Chapter 8

2

Objectives (1 of 2)

Describe relationship of VBA to Microsoft Office Describe components of the Module window Describe two ways to create an event

procedure Explain how the Quick Info and Complete Word

features simplify entry of VBA statements Create a combo box to locate a record on a

form

Exploring Microsoft Office - Microsoft Access Chapter 8

3

Objectives (2 of 2)

Describe MsgBox parameters

Create an event procedure to facilitate data entry through keyboard shortcuts

Create an event procedure that substitutes an application-specific message for the standard Access error messages

Describe several types of data validation

Exploring Microsoft Office - Microsoft Access Chapter 8

4

Overview VBA is a programming language to

build truly useful Access applications

VBA is event driven: Procedures respond to specific events

VBA can modify procedures that Access has already created

Provide an appreciation for what can be accomplished with VBA

Exploring Microsoft Office - Microsoft Access Chapter 8

5

Introduction to VBA

Data validation

Facilitate data entry, including creating keyboard shortcuts

Error trapping

Enhance communication with the user by using message boxes

Exploring Microsoft Office - Microsoft Access Chapter 8

6

Modules and Procedures

Visual Basic code is developed in units called procedures

Event procedures: run automatically in response to an event

General procedures: called explicitly from within another procedure

Exploring Microsoft Office - Microsoft Access Chapter 8

7

Modules All procedures are stored in modules; one

module contains one or more procedures Every form in Access has its own module

(Class module), which contains procedures for that form

Private procedure: accessible only from within the module in which it is contained

Public procedure: accessible from anywhere

Module window: where procedures in a module are displayed and edited

Exploring Microsoft Office - Microsoft Access Chapter 8

8

Module WindowName of procedure (Form_Close)

MsgBox statement

Name of nextProcedure (Form_Current)

End of procedure

Exploring Microsoft Office - Microsoft Access Chapter 8

9

MsgBox Statement

MsgBox takes three arguments (known as parameters)

Prompt: Specifies the message text

Buttons: Type of command buttons and icon

Title: Text that appears in title bar of the message box

Exploring Microsoft Office - Microsoft Access Chapter 8

10

Create an Event Procedure

Select Event tab

Click On Current Select Code Builder

Right click onForm Selector box and choose Properties

Exploring Microsoft Office - Microsoft Access Chapter 8

11

On Current Event Procedure

Procedure header

Name of ComboBox from step 3

Complete Word willprovide completionoptions

Exploring Microsoft Office - Microsoft Access Chapter 8

12

Facilitating Data Entry

Use the Default property to specify default values for certain fields

Use VBA to create keyboard shortcuts

A KeyDown event procedure can implement keyboard shortcuts

Exploring Microsoft Office - Microsoft Access Chapter 8

13

KeyDown Event Procedure

Select Form in theObject list box

Select KeyDownfrom the Procedure List box

Key wordsAppear in blue

Exploring Microsoft Office - Microsoft Access Chapter 8

14

ShortCut Command ButtonSelect the command button Properties All tab

Change Name toShortCutButton

Change Caption to&ShortCuts

Command Button tool

Exploring Microsoft Office - Microsoft Access Chapter 8

15

Error Trapping Produce more user-friendly error message Find the error number using the

Immediate window Use case statements to test the value of

an incoming variable and produce the appropriate statement

Once error is detected, Call MsgBox statement to display your user-friendly error message

Else will execute if all Case statements fail

Exploring Microsoft Office - Microsoft Access Chapter 8

16

Error Event Procedure

Case 1

Error numbers

Case 2

Else statement

Exploring Microsoft Office - Microsoft Access Chapter 8

17

Data Validation

Invalid data corrupts validity of information

Data validation is therefore crucial Use VBA to extend data validation

capabilities within Access Use a nested IF statement to

remind users to leave no fields empty

Exploring Microsoft Office - Microsoft Access Chapter 8

18

MsgBox Function vs. Statement MsgBox function: displays a

prompt to the user, then returns a value- Requires parentheses around arguments

MsgBox statement: simply displays a message, does not use parentheses

Exploring Microsoft Office - Microsoft Access Chapter 8

19

Chapter 8 Summary (1 of 2)

VBA is a subset of Visual Basic

VBA is accessible by all Microsoft Office applications

All VBA procedures are stored in modules

Every form in Access has its own module that contains the event procedures for that form

Exploring Microsoft Office - Microsoft Access Chapter 8

20

Chapter 8 Summary (2 of 2)

All procedures are either public or private:Private—accessible only from within its module public—accessible from anywhere

Event procedures were created to illustrate how VBA is used to improve an application

MsgBox function has three arguments:message, intrinsic constant, and title bar message