Limiting a computer controlled unit's movement

I'm having trouble figuring out how to restrict the computer's movement to only within the invisible blue circle around its unit. I plan on this game being a turn-based strategy where the computer will move to the closest point inside the movement circle to a player's unit each turn, then when it is close enough to attack, it will.

http://dl.dropbox.com/u/42269734/MergerWars.capx