Modifying the Shopping Cart Tutorial

I'm trying to modify the shopping cart tutorial to fit my existing website.

I am currently using PHPNuke with a Gallery module to display photos. I'm trying to sell the photos and I'm currently using a Paypal hack that uses Paypals shopping cart. The way it works is:

I pick a product out of the dropdown and it launches paypals cart with parameters from the photo chosen (photoid, album, price, etc). The problem is that Paypal doesn't allow international users to use the shipping profile therefore it doesn't quite work for me.

I need to add a description field to the cart table and record which photo/album was chosen. Then check to make sure the same photo hasn't been chosen again when displaying the shopping cart. I thought this would be fairly easy by just adding another variable wherever "qty" and "itemid" was found. But no luck. The code to my Cart.php is attached.

Andy