Set angle rotation limit without physic plugin

Well title is obvious.

I have an rotating object:
 

object.rotation=0-obj2.y

The object rotates its self when obj2.y change.

However I want it to rotate between -180 and 0.

I know there is a rotation limit in the physics plugin but I dont want to use it.

Anyone know how I can set a rotation limit?

Check the rotation in an enterFrame listener and change it if it exceeds those bounds.

Check the rotation in an enterFrame listener and change it if it exceeds those bounds.