Excel is your friend … quite a remarkable tool actually … you can always use the free version called OpenOffice. 8-p
Seriously though … just put columns on the top for the game … rows represent the quarter … enter your total gross and use a formula to calculate it. It should not take you more than a few minutes each quarter. Most places you sell from will give you sales figures … you could literally just plug that in.
I honestly don’t see it as a problem … and when you hit it big you can always hire someone to do it for you. 8-}