In a tutorial I wrote a while ago, I had an AIPlayer that would rotate a ship to face another ship.

There's a function that figures out what the angle is between the AIPlayer and the its target, then another function (called faceAngle) which will the make the player start turning in that direction.

So go here:

http://www.flashgametutorials.blogspot.com/

scroll down the AIPlayer class, and find the function faceAngle(), and that could point you in the right direction...