如何将可变数量的用户定义数据发布到Paypal？

Friends, I have some shopping cart code that I took over when I started with a company, but unfortunately I'm weak on Java and integrating with Paypal. Here is the form that sends data to Paypal when a customer checks out of the shopping cart. I can get it to send one product, but I would like it to include data on all the products purchased from the cart. I am thinking logic:iterate will help me? But then how do I increment the "on#" and "os#" when presented with a variable amount of products?Friends, I have some shopping cart code that I