How can you tell if a gameobject is looking directly at another gameobject?

I'm using a coroutine to make a troop look at the enemy troop when it is within a radius, I want the troop to look at the gameobject. Is there a way to tell if the gameobject is looking directly at the other gameobject so I can stop the current coroutine and move to the next coroutine?

 public IEnumerator LookAtEnemy()
     {
 
         Debug.Log ("Started");
 
         yield return new WaitForSeconds (1);
 
         //while (//Repeat until the object is staring at the object...) {
         
 
             if (this.gameObject.CompareTag ("ShootingFriendly") && SightS.EnemiesInRange.Count > 0) {
                 {
                     Debug.Log ("Turning");
                     GameObject CurrentEnemy = SightS.EnemiesInRange [0].gameObject;
                     Quaternion Rot1 = Quaternion.LookRotation (CurrentEnemy.transform.position - this.gameObject.transform.position);
                     this.gameObject.transform.rotation = Quaternion.Slerp (this.gameObject.transform.rotation, Rot1, Time.deltaTime * 3);
 
 
                     Quaternion Rot = Quaternion.LookRotation (CurrentEnemy.transform.position - Gun.transform.position);
                     Gun.transform.rotation = Quaternion.Slerp (Gun.transform.rotation, Rot, Time.deltaTime * 3);
                 }
 
 
             //}
 
 
         }
 
     }