Can I give a discount to an affiliate instead of money back?

Hi, I run a non-profit site where people can buy a membership (using Paid Memberships Pro) to help support our programs and our work.
Instead of paying affiliates for each new member they recruit, I would like to give them a discount that they can apply to their own membership renewal fees. Possibly something like: If you get 5 people to register, you get one year free.
Is this sort of setup possible with your plugin? If it is, how would I go about implementing it?