Automating Tasks with Visual Basic

Introduction  When can’t find a readymade macro action that does the job you want, you can use Visual Basic code.  Example: − Modify a whole batch of records at once. − Perform complex calculations. − Interact with other programs on computer. − Write even more complicated validation routines that lock out bad data.

Understanding VBA Terminology  Some basic VBA terminology: − Statement: A word or combination of words that constitutes an instruction to be performed by the VBA engine. − Procedure: A collection of VBA statements that are grouped together to perform a certain task. There are two types of procedures:  Subroutines: perform a single task, no return.  Functions: perform a task and then return a value

Understanding VBA Terminology − Module: Procedures live in modules. A module consists of one or more procedures − Variable: is nothing more than a name applied to represent a data value. Variable is used to hold values such as customer names, dates, and numeric values manipulated by the VBA code.

The Visual Basic Editor  Visual Basic code is stored in database, but it need a different tool to view and edit it, called the Visual Basic editor.  Open the Visual Basic editor:  In the Access ribbon, choose Database Tools ➝ Macro ➝ Visual Basic

The Visual Basic Editor  The Visual Basic editor window is divided into three main regions. − Project window: shows all the modules in your database. − Properties window: which shows settings for the currently selected item in the Project window. − Document window: Edit code region.

Adding a New Module  In the Visual Basic editor’s menu, choose Insert ➝ Module.

Adding a New Module  When add a new module, the Visual Basic editor automatically opens a code window that shows the contents of that module.  Initially, a brand-new module has just one line of code: Option Compare Database − This line is an instruction that tells Visual Basic how to handle operations that compare pieces of text.

Adding a New Module  Before write code you should add one more instruction to the top of code file: Option Explicit  This instruction tells Visual Basic to use stricter error checking, which catches common typos when using variables.

Simplest Possible Code Routine  Every module are one or more subroutines. A subroutine is a named unit of code that performs a distinct task.  Subroutines start with the word Sub followed by the name of the subroutine and end with the statement End Sub  Example: Sub MyCodeRoutine() MsgBox "Witness the power of my code." End Sub

Module types  Access stores code in two places: − Class modules: attached to the form or report, it executes when the form or report is opened, the class module does not appear in the modules section. − Standard modules: Code can also be stored in modules section. Standard modules is accessible to all objects in your database.

Responding to a Form Event  Open a form in Design mode.  Turn off Control wizard button.  Add a new button.  Inthe Property Sheet, choose the Event tab, and then select the button’s On Clickevent  Click the ellipsis (…) in the On Click Event box  Select Code Builder and click OK