MS Access

I'm currently developing a project on MS Access 2003 and I stuck at a particular point.

I have created a form "student payment details". Within that form I have inputted a combo box, where user is able to click on the combo box and from the drop down list user selects type of payment made by student either Credit card or Cheque.

I have also created forms for Credit Card or Cheque payment details individually, and I have also crated individual macros for the forms to open up when I run the macro.

But what I can't do is link the macro within the combo box, so when user selects either credit card or cheque from the list...I want the forms for either credit card or cheque forms to open up automatically...depending on the type of payment is selected...please help??

many thanks

Regards

Vimal