Need help with a complex shopping cart rule

Question

I have a shopping cart rule and I haven't been able to figure out how to make it work. Any help would be appreciated.

Here it is:

A customer can buy 2 skus from a category, but they must not be the same sku. If they do, they get a third, specific sku at a discount.

The first part is the part I'm stuck on. How do I make a rule for 2 skus from a category that are not the same product?

Thanks!!!

Answer 1

The only solution I see is, to generate every combination. if you have four products: A,B,C,D and Z for a discount something like:

IF A and B or A and C or A and D or B and C or B and D or C and D

This is a lot, if you have more than 5 oder 6 products and will make your store terrible slow, so don't do it if you have more than a few skus.