This might be possible already, but haven't had a chance to test what we want as we have an existing DKP table I don't want to break or flood with a bunch of test data. We want is to allow folks to always be able to bid the minimum bid value per slot, or up to their maximum available DKP.

Example:
Player 1 = 100 dkp
Player 2 = 10 dkp
Item = 20 dkp minimum bid value
Player 1 can bid from 20 to 100 dkp, but not over 100. Player 2 can only bid 20 dkp, and they end up at -10 dkp.