I already have a shopping cart designed. I purchased shop-script pro shopping cart software and all I need to do is insert the necessary code to my "add to cart" buttons. Once these buttons are pressed the item is added to cart.
Except the shipping modole, I don't need most of the options in the shop-script templates, As describe about, I would like to have the catalog outside the cart and just link it with the cart system where shipping/billing would be used.