PayPal Chained Payments with MultiSite/Framemarket

Hi, we are trying to build an "Etsy style" marketplace using MultiSite, BuddyPress and Framemarket/Gridmarket. We need to implement PayPal Adaptive Payments for Chained payments so that we can take a percentage of each sale. I'm at a dead end here and can't figure out how to do the PayPal piece! Can you help please?