Filtering a subform

[karen s via AccessMonster.com]

I have a filter selection screen that allows the user to select a division
and a customer. If no selection is made, all is assumed. Once the selection
is made, I open a mainform that contains a sub form. The mainform's
recordsource is set on open of the form depending on the filter selection
screen.

The subform is linked to the mainform by division and customer. The
subform's recordsource is a saved query that returns the detail invoice
information. This is working as expected and only the invoices for the given
selection are shown in the subform. If no selection is made, the mainform
navigates through all divisions/customers and the subform is linked and
dynamically changes.

I need to add a combo box on the subform to allow the user to select an
invoice. If the user knows the invoice number, I want him to be able to
enter it or select it and the subform returns only the selected invoice. If
the user leaves the invoice combo box selection blank, all should be returned
and the master/child link will keep the forms in sync. The invoice selection
can not be on main form because the main form summarizes on the customer.

I am having a mental block with this one. Any assistance would be
appreciated.

Thanks.