PhilWilky
It's easier when we can see the CAPX, but I think I get it now. You need to compare the frame when occurs collision between the sprites.
Event: Sprite (hero) >> On collision with another object (on collision with enemy)
Subevent: Sprite (hero) >> compare frame (= Animationframe hero / sword frame number)
Action: Destroy enemy
I hope now your problem has been solved.