|To use F8, you typically place your cursor anywhere within the code and begin pressing F8 to single step. This will highlight each line just prior to execution.|
That said, there are certain types of subs that F8 doesn't work with directly. The KeyUp event is one of those.
What you can do in these cases is simply turn the sub into a "normal" routine by changing its name to something like Sub MyTest().
You may have to comment out lines like If KeyCode = 13 Then and it's associated End If, but once your turn it into a "normal" routine, it should single step fine.
BTW...You can create watches by opening the Watch window and dragging variables (e.g. sht.Name) into it to see their value as you step through the code. Further, you can create Watches on "variables" that aren't in the code to show you more detail.
For example, you could add a watch for ActiveCell.Address so you could tell which cell Excel will be working on at any given point.
Finally, there are certain variables that you can see the value of by just hovering your cursor over while single stepping. e.g. "c" in your code is one of those.