I have one field on a form with a drop down list and choices are "1", "2", "3". If 3 is picked then I want to force the user to put in a value in a different field on the form, without always forcing it. The user must be able to leave it blank at times. Also, if 1 or 2 is picked then I want the different field to only allow certain values depending on what is selected in the first one.

Thanks ahead for any help!

Put your edits in the BeforeUpdate event of the form. If there is an error, you can display a message box, put the cursor in the field that needs fixing, and cancel the update event.