I have a shop setup, it works fine. I used a template and it works through paypal shopping cart.

What I want is to be able to use coupon codes and/or discounts at the checkout page. I do not want to resetup my products page I just want to be able to utilize coupon codes, discount codes, and an affiliate ID although the affiliate ID is not necessary.

Does anyone have any suggestions as to what would work well for me?

It doesn't have to be a free program, just something that falls within the parameters.

I am using godaddy linux hosting.

Please help!