Dates Validation in Access 2000

When I enter a date Ej. (33/33/2003) in a text field “Formatted as Short Date” in a form. I received the system error.
I want to be able to eliminate the system error and make a Custom error message. I have try to make a sub procedure in VB and place it in the method “Before update, After update, on focus, on lost focus …” but nothing works.
Access detects the error before leave the text field and don?t pass control to the procedure in order to detect the error. Giving me the system error.
What can I do too make access pass control to the VB Sub form to validate the error.
Please gave me an example of the validation code that I cut use.