I have a set of tables for provinces, their divisions, subdivisions etc and a form where user chooses province, etc. As he does this, the subordinate comboboxes need to change their rowsources and the controlsource value, which normally becomes blank.

Take a look at Chapter 5 of "1001 Things". There is an explanation on how to do this and a code sample as well.

I am looking forward to seeing you again at SWFox in October!