What is the best way to show "exactly two" using predetermined predicates in propositional logic?

Question

I need to make a proposition saying, "exactly two will do it" using only the 4 predicates A, B, C, and D where A = "A will do it," B = "B will do it," and so on. All I've been able to come up with is (A^B) OR (A^C) OR (A^D) OR (B^C) OR (B^D) OR (C^D), but I don't think this exactly translates to "only two will do it." Is there a better way to go about this?