I've made an animation where a charakter walks and holds a weapon with his hand. Then I wanted to move the hand up and down with a script so the arm angle is always the angle, where the camera looks. Unfortuntely, it didn't work well. Unity can't decide what it should make, fbx or script? So the arm jumpes around. How can I solve it?

var cam: Camera;

var Arm : Transform;

function Update () { transform.rotation=Quellobjekt.transform.rotation; Arm.Rotate(50,0,0); }