left/right rotation force

Hi to all, I've created a script that makes a half a turn on right and left if i press a key. How can I do for give force with 2 keys? Movement is similiar to swing.. if I relase keys, the position return to original position.. would that it were: Press taste1 = left rotation; Press taste2 = right rotation

void Update() { //-- arm rotation float arm_rot = Mathf.Sin(gondelarm_sin) 80.0f; gondelarm_sin = (gondelarm_sin + Time.deltaTime 1.0f) % 360.0f;

  gondelarm.transform.localEulerAngles =

new Vector3(0.0f, 0.0f, arm_rot); }