Is This Possible? Different referrers, different skins

[The Equivocate]

I'm opening a forum that will act as the "central" forum for a bunch of different sites. As I don't own most of these other sites, we're going to split the revenue based on what sites are referring. Ideally, I'd like to have different preset referrers/domains. Then, based on where the visitor comes from, they get the skin branded with that referrer/domain.

However, this only is half the idea, because I also need a way to associate returning members/posters with where they came from. So, if Visitor comes from Affliliate A and signs up, and then a few weeks later they visit the forums from Aff. B, Aff A still gets the credit for the page views (and then the ensuing ad revenue). The ads themselves seem easy to do as each affiliate will have their own skin anyways, so just put the adcode associated with that affiliate in that specific skin.

The only question I have is how to force a skin on a user based on their referrer, and force them to keep it. That would be the easy way, but I'd also like to be able to sort members by referrers. Possibly put them in groups, but then if I have 20 different regular member groups, it's going to get annoying, especially with permission-based adjustments.

Basically I want to make sure each referring affiliate is getting the credit and getting their share of the profits based on how much traffic they're sending.