User defined price with multiple digital downloads

I looked over the support area and could not find anything related to this.. I am using the latest wp3.51 and cart66 lite 1.5.1.2. I have it set up for users to define their own pricing. I did a test with one file without a price and received an error which I was expecting. Then I decided to test using multiple purchases at the checkout, one with a price and one without on the same order. I was able to process through paypal sandbox testing and made the payment. I was sent the links were I was able to get both files to download. I am not any type of web-designer/programmer. If anyone could help I would appreciate it very much… Thanks you in advanced for all the help…

http://wordpress.org/extend/plugins/cart66-lite/