How to fix Child Object Rotations.?

Hello Everyone,
I put here one empty game object and inside i put 1 ball as a child and i put 1 more cube as child inside this empty game object i want only ball should Rotate but my cube is also Rotating with this Empty Game Object.
How can i fix the Rotation of cube it is child of Empty game object , can i fix the rotation of only cube?

Maybe use this:

var cube : GameObject;

// add your part here

cube.transform.rotation = 0

tell me if it worked