I used Ron's formula below, with success, but I would like something little
different.

I would like the B1 cell (dependent list) to be blank if the A1 cell is
changed after the B1 cell has been completed.

So, a user enters a value in A1, the list in B1 is restricted. They select
something from B1. They they go back to A1 and either change the value or
delete the value - at this point I would like B1 to go blank.

Any ideas?

THANKS