What you describe makes me think of a combo whose AfterUpdate event rebuilds the list to show second level items based on the first choice. Now you need a way to reinstate the first list. Reset button? Theory not tested, but I don't see why it couldn't work. It would require more work than adding the second combo, which you didn't seem to want to do. The combo could never be bound to anything. All in all, I agree with the previous answer - just thought I'd throw the idea into the mix.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.