Hello Tom.

I have put a customized event into the form where it is activated on the click event of combo A.

You are going to be better of to set this up once in a custom method called from the form's Init(). This only has to be done once. WHy do it every time the user clicks on the 'parent' combo? Or is your application running a little too fast and you need to slow it down a little < g > ?

.controlsource = positions.contact1id

The only thing I can think of here is this: Are the field widths of Contact.ContactID and Psotions.ContactID the same?