Paypal integration with existing PHP API

I need some php pages that will sell software license keys. The keys are issued by the software author and the API to complete the transaction is available <a href=[login to view URL]>HERE</a>. Page One: A form to collect the following: Name Email address MikroTik user ID (optional) Software Level Requested with price pulldown list Software ID1 Software ID2 Software ID3 Software ID4 Software ID5 Software ID6 Software ID7 Software ID8 Software ID9 Software ID10 The user can enter up to 10 software ID's which are used to generate the keys. On submit, they are taken to PayPal where they will pay their fee based on the number of software ID's multiplied times the level of license (price) they selected. All ID's will have to be the same license level (price). They complete the paypal transaction and then are returned to the MikroTIk API which gives them their license keys. All programming is in php to run on apache/linux.