Is there an option to pro rate the shipping costs

My customer is requesting that they be able to Pro Rate the shipping cost.

They state that they want it to work the same way that works. In other wards.

you pay 5.00 for shipping on the first item. then 2.50 for each additional item
then also be able to do the same for

and International
(obviously the shipping cost and pro rate are to be form feed values.)

Is this possible? I did not see this option currently in the latest version. If it is not is it soon to be available or being worked on?

If im out of luck I happen to be a fairly average php programmer and would not mind taking a shot at this my self. Which file or set of files currently hold the functions for shipping in marketpress?