VBA listbox problem

I have a database that has two main tables: Vendors and Contacts. On the main form Vendors, I have some textboxes that show information about the vendor, and then a listbox that is bound to a query that filters all the contact names by the corresponding vendor. The query takes it criteria from the vendor name textbox on the form. The query works correctly when I test it.

My problem is that when the form opens, the listbox shows the correct contact names for vendor record 1, but when I navigate through the database, the names in the listbox do not change; the listbox continues to show the contacts for vendor record 1.

I've tried running a requery macro for the query that the listbox is bound to. I've tried using it on the change event for the Vendor name textbox, and with On Dirty event for the form. So far, no luck. Can someone tell me what I'm doing wrong?

Lee