I used a google doc to split some payments when I went cottaging last week, so this is exactly what I was looking for. Pretty much: I drove person X and Y, so they owed me for gas, but I also bought food for 6 people, so they all owe for food, but 3 others bought food - so you write X and Y in the last column for gas, but "all" for food, for myself and those 3 others. Forget the buttons, just tab across the fields and the Ajax sorcery takes care of splitting up the bills, really handy +1.