custom protected downloads script

I simply need a script that will allow me to add downloads to pages on my site. the script needs to be able to protect the downloads until the customer has paid via paypal shopping cart. I want the script to be server side only so php or similar. it must be easy to add the downloads with none - or at the most, simple coding required. please bid sensibly or not at all, i am aware that there are free scripts out there for this type of thing but they do not do enough for what I need.