[AccessD] DependentObjects class

I am working on a dependentobjects class, i.e. a class with a collection
which holds objects (classes) where the control or form is dependent on the
current control.  Combo A changes.  Combo B uses Combo A to filter itself.
Combo B is "dependent" on combo A and must be requeried whenever Combo A
changes.

There is a case where two combos on a form may display data from the same
table.  For example two combos both display cities from the cities lookup
table.  If Combo A NotInList adds a new city. Combo B needs to requery in
order to display that new city if necessary.  However if Combo B adds the
city, then Combo A needs to requery.

Obviously if we add combo A to combo B's DependentObject collection and we
add Combo B to Combo A's dependent object collection, then we start an
endless loop where A requeries B which requeries A which requeries B...

This is a case where I programmed a solution working but it was ugly.  How
would you solve this problem?

John W. Colby
www.ColbyConsulting.com