commission on individual (with-in) membership

In our salon when a client uses their membership, we would like for the stylist to get the commission off of one membership used not the entire. example: our blowdrys are $35, we sell the memberships 5 for $150. So, within the membership it would be $30. I would like my stylist to get the commission off the $30 not the membership price. It would be beneficial.