Set up productset promo

I am trying to set up a promotion on product set: Get a 10% discount when you buy a total look. 

For this promotion I would think to go for the promotion Buy X and Y and get Z. This works fine when the promo is active on 1 productset, but not when you want this promo active on all sets. All items that are part of a product set do then get a discount, however we want to make sure that the promo is only active when a customer buys the entire set. 

How can we set up this promo that it is active on all sets and yet only qualifies when a customer buys the entire set?

thanks in advance!