Another alternative is to use stuff that people have crafted that is different from what PayPal offers. No disrespect to PayPal, but there are other alternatives. Here is one I offer for free...
http://members.aol.com/paypalhelper/auto.html
It lets you stuff info into any PayPal field you want, and create complex description or options fields. Your only limitation is the length of the fields that PayPal offers (127 for description, and 200 for each of the options fields - and some other stuff).
All you have to do is to understand the "calls", and what they do. The article that starts it all is...
http://members.aol.com/paypalhelper/
Understand PayPal first, then you can understand what I am doing with it to permit people to increase functionality.
Ron.