How do I have an object that's pinned at a distance move around the area toward the player position?

I have an eye, and I have the pupil as a separate object that's pinned to the middle of the eye and I want the pupil to follow the player's position like its looking at the player, my trial and error led to my posting of this

You will need to play with sin & cos: dropbox.com/s/3zgbpglycbjwv0o/looking_pupils.capx