Content/Download Locking Type Script

I need a script that can do the following. *note this is not a gateway or content blocker, i dont want that. *also note I dont know what this would cost to make, how hard etc. Give me a realistic quote. What I need is a script that allows a user to navigate my page freely, read onscreen text etc. however the download button wherever it may be on the page is "dulled" out and unclickable until my affilite link is clicked, and completed. If they click the link and dont complete the offer, its still dulled out. However if they complete the affiliate offer ( its one page, so first submit ) the download link on my page becomes active and they can download the product for free :). I'm not very good with coding, so i dont know if this is possible or not, but im thinking it would somehow have to know when the submit is pressed on the affiliate link page so it knows that the offer was completed and they get their free download. Also 1 download per ip would be ideal. ( i wont be reselling this, it would be for personal use ). Please, id love a quote.