Game Server price calculator.

I need a script written that will calculate the prices of my game servers. There will be multiple forms per page therefore the script will need to be able to work with any field/form. My idea is to have the person choose a location. The location will have a % linked to it so it can adjust the prices accordingly depending on location. Then prepay will be a % also that will reduce or added to the price. And finally the players, this field will hold the cost per player. The major thing I'd like done with the players field is, when a person selects the player size it updates the cost difference between the other player sizes. Example --16 Player(Default) Slot Chosen-- 16 Players 24 Players +12.00 32 Players +26.00 --24 Player Slot Chosen-- 16 Players -12.00 24 Players 32 Players +14.00 and all at the same time updating a chosen total field within the form. The link to the current design for the form is: [login to view URL];sub_zone=game_servers