What is the best approach to provide for two different SQL SELECT criteria for a ComboBox RecordSource?

For example, suppose you have a form with two ComboBoxes:

  
Control     Control Source       RowSource
cboState    Customer.State_ID    SELECT State,State_ID from States
cboCity     Customer.City_ID     SELECT City,City_ID from Cities
<\pre>

What I'd like to do is for the cboCity do display one of the following lists:

(1) IF the cboState control source (Customer.State_ID) is 0 or empty, show ALL cities for ALL states 

(2) Otherwise show only the Cities whose Cities.State_ID = Customer.State_ID entered in the cboState control.

I know how to write the SQL SELECT for both of these cases, but how do I change the RecordSource of the cboCity control during runtime?

TIA,
jmu

Best Regards,

Jim Underwood
Apollo Information Systems, Inc.
Houston, TX