If I'm understanding correctly (and it's possible that I'm not), there are a few ways to do it.
1) Check which direction you're moving in (clockwise or counter), detect the collision, and then change directions appropriately. For instance, if you're set up to move clockwise, you're currently moving to the right, and you have a right side collision -- update the movement to move down. If you then collide on the bottom, update the movement to move left.
2) Hardcode the offset values from the origin. For instance, it's now 200 horizontal pixels from the origin - now move down instead of to the right. Ok now we're 200 pixels vertically from the origin, now move left, etc...
3) (Plug) Use the cutscene pack. Place motion (or message) triggers in your scene that will tell your enemies when to change directions. This may not be feasible if you have a large number of enemies in your scene.