Each time someone pays you, you can log that as a distribution. Then you could check to see if any distributions are missing. And if you use the Totals page to manage payouts after a gig, this will automatically balance out if someone doesn't pay you back for the rehearsal space -- that person will show as being owed $20 less at the next gig. In fact, if you gig often enough, and don't mind fronting the money, it might be easier just to let BandHelper deduct those expenses from the gig payouts, rather than having each band member pay you for the rehearsal space.