Bone Rotate Only in it's local Axis

I’m trying to get Spine to look at the center of the screen, but when i rotate up the camera, the spine bone only rotate in it’s local X axis. It seems to be a stupid question, because i use the “SetBoneLocalRotation” function, but… how can i rotate it in the exact direction?

Vector3 CenterScreen = new Vector3(GameObject.FindWithTag("CrossHair").transform.position.x,GameObject.FindWithTag("CrossHair").transform.position.y,Camera.main.farClipPlane);
                 Vector3 point = Camera.main.ScreenToWorldPoint(CenterScreen);					
                 Vector3 forward = (point - animator.GetBoneTransform(Spine).transform.position).normalized;
                 Vector3 up = Vector3.Cross(forward, transform.right);
                 Quaternion rotation = Quaternion.Inverse(transform.rotation) * Quaternion.LookRotation(forward, up);
                 animator.SetBoneLocalRotation(Spine, rotation);	

I solved it by myself… i post the code, maybe i can help someone…

    void OnAnimatorIK()
    {
        if(animator) {
				 Vector3 CenterScreen = new Vector3(GameObject.FindWithTag("CrossHair").transform.position.x,GameObject.FindWithTag("CrossHair").transform.position.y,Camera.main.farClipPlane);
                 Vector3 point = Camera.main.ScreenToWorldPoint(CenterScreen);					
                 Vector3 forward = (point - animator.GetBoneTransform(Spine).transform.position).normalized;
                 Vector3 up = Vector3.Cross(forward, transform.right);
                 Quaternion rotation = Quaternion.Inverse( animator.GetBoneTransform(Spine).transform.rotation) * Quaternion.LookRotation(forward, up);
                 animator.SetBoneLocalRotation(Spine, rotation*Quaternion.Euler(0,40,0));	                
        }
    } 

The problem was in “QuaternionInverse” where I had put the main Parent rotation instead of animator.GetBoneTransform(Spine).transform.rotation.
Also i add Quaternion.Euler(0,40,0) to correct the rest of the upper body which was slightly rotated in another direction than the spine, caused by the type of animation