Limit downloads to 1/user

Does anyone know of a plugin/script/hack that limit the times a file can be downloaded to one per user.

My plan is to offer coupons to members using membership plugin, and I would need some kind of download manager.

Say you have a coupon that you want to offer your users, but you don´t want a single user to download 1000 coupons and sell them on ebay. How would you solve this issue?