Controls and Events

The Next Step

• In the first module, we discussed general problem solving

• In this module, we’ll apply what we learned, from specification to design to implementation and testing, on a very simple process

• Later we’ll gradually introduce VB features that let us implement more complex processes

But First…

• We have to learn enough about VBA and Excel to write an interesting program!

• So our goal in this module is to learn those basics and apply them to a problem

Relating VBA to Processes

• We will typically represent the objects in our process specification by Excel or VBA controls and other Excel and VBA objects

• Objects and controls have events associated with them

• The process events will be translated into control events for which we will write procedures

Writing a Macro

• We’re going to start by writing (not recording) a small macro with a button to control it

• This will introduce a number of basic concepts

The Code

Option Explicit'*****************************************' Turn the active cell red'*****************************************Sub RedCell() ActiveCell.Interior.Color = vbRedEnd Sub

The Video

• You can watch the steps of writing the macro and adding the button on the video called Button Demo

• The workbook is available on the class site• After you watch, try writing your own macro,

say GreenButton, in the same worksheet. Give it a button and/or a piece of clip art to activate it

Events

• Clicking the button or the clip art is an event that triggers the execution of the macro

• This is a pattern we will continue to follow: our macros will be triggered by events that happen in the spreadsheet

• Later we will also write macros that can be called by other macros

Referring to Objects and Properties

• Consider the expression ActiveCell.Interior.Color = vbRed• ActiveCell is an object recognized by Excel: the cell

that has been selected in the active worksheet• Interior is a subobject of the ActiveCell: it’s just

the interior of the cell• Color is a property of the Interior, and as such can

be set to a value by an assignment statement

Properties vs Variables

• We’ll often be setting the values of properties of objects

• Cells in particular have a property called the Value: ActiveCell.Value = 5 will make the number 5 show up in the cell

• Besides properties of objects, we’ll also use more general variables for quantities we want our program to remember and work with