I've tried Overture Pay Per Click for the last month

I've tried Overture Pay Per Click for the last month now but the thing that strikes me is I have no way of tracking sales per keyword. I have affiliate software which *could* do this but it would mean an affliate account for each keyword/phrase which would be ludicrous bearing in mind I am experimenting with about 20 to 30 keyword phrases and possibly looking at other Pay Per Click engines. Is there a recommended script that will do this (free or otherwise). What I'm looking for is software/script that will tell me Overture made a total of X in Y month, with a breakdown of each keyword/phrase sales. Any suggestions?