Rotating arm with Animation Event

I want to do the arm following the mouse, but a bit different. So I figured out that what I needed is an Animation Event. So I programmed the code and inserted the event and it doesn't work! It's a puppet character.

Transform Tree:

 -Player
   -Body
     -Head
       -Face
     -Left Arm Upper
       -Left Arm Lower
         -Left Weapon
     -Right Arm Upper
       -Right Arm Lower
         -Right Weapon
     -Left Leg Upper
       -Left Leg Lower
     -Right Leg Upper
       -Right Leg Lower

  

Animator is on the Player. I made a code into the PlatformCharacter2D, so it can show into the animator:

 void AimLeftArm () {
         Vector3 difference = Camera.main.ScreenToWorldPoint (Input.mousePosition) - LeftUpperArm.position;
         difference.Normalize ();
         
         if (LeftUpperArm.transform.root.localScale.x == 1) {
             float RotZ = Mathf.Atan2 (difference.x, -difference.y) * Mathf.Rad2Deg;
             LeftUpperArm.rotation = Quaternion.Euler (0f, 0f, RotZ);
         }
         
         else if (LeftUpperArm.root.localScale.x == -1) {
             float RotZ = Mathf.Atan2 (difference.x, -difference.y) * Mathf.Rad2Deg;
             LeftUpperArm.rotation = Quaternion.Euler (0f, 0f, -RotZ);
         }
     }

But it doesn't move the arm!