Electric Fence

So for my mod ArchaiCraft, I made 7 custom blocks intended to be used for making a redstone powered Electric Fence, based off the Jurassic Park fences (Base, Base corner, Pole, Pole corner, Pole lights, Pole lights corner, and wire), when placed in a certain way they resemble said JP fences, and I tried to make them redstone activated, so that the wire hurts entities that hurt it, but I after much trial and error I can only make the wire always hurt the player or not at all.

If anyone has any idea how to make it so that when powered, the wire hurts entities, but when not powered, it only stops entities from going through it, I would appreciate it if you showed me how.