Animation: Object distance determining frame?

Hey, guys.

Right now, I'm attempting to create a little fishing minigame, and am trying to add a bit of animation to the pole. It has an animation where it's bent all the way to one side, then straightens out, and then bends the other way.

What I want to do is have it register the position of the fish it would be attached to, and then have said fish's distance to the left or right of the end of the pole determine which frame of the animation the pole is on; if it's directly in front of it, it'll be at frame 10, where it's straight. If it's somewhere over to the left, it'll be around frame 0, where it's bent that direction.

Any ideas?