Step Through Code

When you are writing or maintaining code it is very useful to be able to step through the code one line at a time.
This can help you see what each line of code is doing and can help you understand complicated blocks of code.
As each line of code is executed, the appropriate action is taken and the corresponding line is highlighted in yellow.
Pressing F8 will execute the code one line at a time.
SS
Immediately before a line containing a break point is executed the line will appear with a yellow background.

Sub DebuggingThis 
Dim iNumber As Integer 
Dim sText As String 
   iNumber = 10 
   iNumber = iNumber * 2 
   sText = iNumber 
   Call MsgBox(sText) 
End Sub 

Sub MyRoutine 
Dim iLoop As Integer 
   For iLoop = 1 To 10 
      Debug.Print iLoop 
   Next iLoop 
End Sub 

Stepping through code - simple screenshots of the yellow bar
SS -

Once your code has been stopped, by a break point or by stepping through your code you can resume execution by pressing (Run > Continue( or F5. To end the macro press (Run > Stop ??).
This causes execution to stop at the line after the call to this procedure.

Run to Cursor

This allows you to execute code and then enter break mode on the line containing the cursor. This is similar to putting a break point on a line, although "running to cursor" is temporary and will not have an effect the next time the code is executed.
Changing statement execution order: While execution of your code is halted you can control the execution sequence of statements within a procedure. To set the next statement to be executed position the insertion point anywhere in the code and go (Debug > Set next statement) or press (Ctrl + F9). Alternatively just drag the yellow arrow to the corresponding line.

Excessive Debugging

Whenever you are doing lots of debugging it is worth saving your modules (i.e. exporting them) every 10/15 minutes as VBA has a tendency to crash if you are undertaking mammoth debugging sessions.
SS of error message

Important

The line highlighted in yellow is the next line to be executed
All macros can be stopped at any time by pressing (Ctrl + Break).
If a procedure appears to be hanging you can normally interupt it by pressing (Ctrl + Break).