VBA Tab Controls w/ Access 2002

[mehere64]

I have a form in Access 2002 that contains a Tab Control with 4 tabs. Each tab on the form is a subform. I need to validate a specific field on each tab. I created a Public Function for this that works fine. It will not let me off the field until it is corrected. My problem, however, is that it will let me click onto another tab. I need to stop that from happening. I'm using the OnChange Event Procedure, which does pop up my error message, but I can't get the focus back to the tab/text box that caused the error.

Any help would be greatly appreciated.