cubepoints + buddypress

Hi,
I'd like some help with the project I'm trying to create.
Ive seen that with the Marketpress plugin you can combine Cubepoints ...
What I would like is : the members can buy 1 coupon reduction with 50 points that allow a 10% discount on ONE article purchased only (could be whatever article but the 10% apply only on one that they buy) but I cant fugure it out how to set it up, could you point me in the good direction please ?
Thanks in advance,
Ol