I've been searching for a shopping cart that fits my client's needs and cannot seem to find the right solution. Here's the reason:
My client send out discounts to chambers of commerce across the US. These chambers receive a portion of the proceeds based on how much the members purchase.

PROBLEM 1:In order to track this, the customer needs to be able enter the chamber name in a dropdown menu and this information is sent with the order that my client receives. (This is critical)

PROBLEM 2: Some products are priced differently based on area of the country that the chamber is located. So I need to be able to discount by product. If a customer buys products x,y,z, the discount is only on item x.

Any suggestions for a shopping cart? Can be PHP or ASP. Preferrably something easy to use.