Microsoft Access VBA Macro Programming

now,” and then rerun the procedure, and up comes another one! This can be very frustrating,

but the best answer to fixing it is to obey the rules of coding in the first place.

The following types of errors appear when the code is compiled, and are often referred to

as design-time or compile-time errors.

Runtime Errors

Runtime errors occur when your program is running. You could, for example, try to open a

file that does not exist, or attempt a division by zero. Such actions would create an error

message and halt execution of the program. They would not show up at compile time because

they are not breaking any programming rules, but they will prevent the code from running.

Logic Errors

Logic errors occur when your application does not perform the way you intended. The code

can be valid and run without producing any errors, but what happens is incorrect. These are

by far the most difficult errors to locate. They can require a lot of painstaking searching to

find, even using all the debugging tools at your disposal. It is very easy to keep looking at a

few lines of code and thinking, “There is nothing wrong with this. It should give the right

answer.” It is only by looking at each line in turn that you will see what has gone wrong, and

often suddenly realize what a simple mistake it was. You may also run into a situation you

did not envisage when first designing your code.

Design Time, Runtime, and Break Mode

When working on an application in VBA, you can be in three modes:

 Design time When you are working on the code for the application or designing a

form.

 Runtime When you run your code or your form. The title bar of the VBA screen will

contain the word “running,” and at this point you can view code but you cannot change it.

 Break If you pressCTRL+BREAK(pressing theCTRLkey at the bottom left of the

keyboard andPAUSE BREAKat the top right of the keyboard simultaneously) during

runtime, it will stop execution of your code. You can also insert a breakpoint by

pressing theF9 Key. Pressing it again removes it. You can insert a breakpoint from the

VBE menu by selecting Debug | Toggle Breakpoint. A dialog box will appear with the

error message, “Code execution has been interrupted,” displaying several buttons.

Clicking the Debug button will take you into the code window.

When you click Debug, you go into instant watch mode, also known as debug mode.

You’ll be able to see your code, and the line it has stopped at will be highlighted in yellow.

This is the line that is causing the problem. You can place your cursor on any variable that is

82 Microsoft Access 2010 VBA Macro Programming