Differentiate referrals by marketplace?

I have a few different websites which market different marketplaces. Is it possible to find out what marketplace the sign up is for? Just to keep track of which websites are performing better. For example I market themeforest and tutsmarketplace. Obviously I can guess by the referral amount but would like to know which brings in more people.

Thanks in advance.

I think it’s not possible at this time.

Yeah I kinda thought that. Its a shame really. It would be nice to have some basic information about the referrals we create.