Please read my post again. That is NOT where I told you to put the code. I told you to put the code in the FoRM's BeforeUpdate event. You put the code in a control's BeforeUpdate event.
If you use a control's BeforeUpdate event, the code will only run if THAT field is modified. That is why the code belongs in the FORM level event. Then it will run if ANY field on the form is modified.