Any VB program—whether a hosted VBA application or a VB executable—is a collection of modules containing code, graphical user interface objects, and classes. This book concentrates on the language elements of VBA as they relate to both hosted VBA and the retail version of VB. The VBA and VB user interfaces—whether Word, Excel, Project, or a VB form—all fire events that are handled by the code you create using the VBA language. Therefore the code modules within your program are of greatest concern to us here.
Visual Basic code can be split into three categories:
Code you write to handle events such as a button being clicked by the user; these procedures are called event handlers
Custom procedures, where you create the main functionality of your application
Property procedures, used in form and class modules
All Visual Basic language elements work equally well in all three types of procedure. For example, there are no restrictions placed on the type of code you can write within a particular type of procedure. It's left to you as the developer to decide what code goes where.
An event is always the starting point for your procedure. It can be a system-generated event, such as the Form Load event or a Timer control event, or it can be a user-generated event, such as the Click event on a command button.
To code an event handler for a control event, open the form's code window and select the control from the drop-down ...