Go to the procedure with the error and set a Break Point. To add a Break
Point, right click a line of code prior to the one you think may be causing
the problem (i.e. pick a line of code near the start of the procedure) and
go to Toggle|Break Point in the pop-up menu. You can also just click the
gray window bar to the left of the line. A red dot will appear on the gray
bar and the code will highlight in red (unless you've changed the default
color scheme). Now, do what you do to make that procedure run. When it hits
the break point, the code will stop and the code editor will pop-up with
that line of code highlighted. Make sure the Debug toolbar is visible
(View|Toolbars|Debug). If it is, there are 3 buttons on it that show an
arrow and lines of text. The one that will step you through the code one
line at a time is the one where the arrow is coming from the top and points
into the middle of the rows of text. If you click the Play button (left
arrow similar to a CD player) you will resume processing the code normally
until it hits the break point again (if it loops or if you run the procedure
again). Removing the break point when you are done testing is done the same
way you set it.