Change subform based on a listbox on main form ACCESS 2003

I have a parent form that displays customers by their Tax ID's.  However, one tax ID can have several names attached to it.  As I change the combo box Tax IS, the listbox with all the names changes to display those that are associated with this Tax id.  This part is fine.  However, there is a sub-form ont his main form that, as the NAME in the list box changes, I want the subform to display teh details for that name.  So, the subform is not really associated with teh TaxID, is is associated with the names (with their Key ID)  in the LIst box.  How can I update the subform based on the NAME key id, not the main  form's Tax ID?

Sandra