Custom vBulletin Mod - Link Serv Mod via Thread

We are currently running vBulletin Version 3.7.4 and require a mod which will enable us to display a unique link per user who has access to see it. To make it a little easier to understand I will explain how it will be of use to us. We currently run a digital music promotional service via vB where our members are able to access our promo's by replying to a thread via a link (placed in a hide hack). This way, our users are able to give feedback and we keep track of which uses have had access to what material. Due to recent leaks of material, we now are using another system which individually watermarks our files and creates seperate download links per watermarked track. Currently we manually keep track of each different link in a spreadsheet, and PM a different one to each user who replies to the thread. We then manually log the users name next to the link. We would love it if it was possible for a mod within vB to be loaded with say 60 different file links during the process of posting a thread. Then as a user replies to the thread, the mod assigns one of the links to the user and displays it in a part of the original thread post. We would then obviously need the mod to keep a log of which link it served to which user. If say more than 60 users reply for access, the part of the original post that is hidden would then need to say something like 'Sorry all allocated downloads have been used at the moment, please check this thread later for the link' once they reply. We would then need to be able to add additional links to allow more users to download.