crosshairs lock-on trouble . locking on to closest enemy but wont change target

so i created a method by which i can draw a lockon on enemies that are near by . Unfortunately once it locks on to target it maintains that target as the only target. here is the entire code :)

only three (3) main functions.

you attach the script to your player gameobject.

can you help me get this thing to work correctly >.< thanks in advance . and sorry for the messy code ^^

 using UnityEngine;
 using System.Collections;
 
 public class Lockon : MonoBehaviour {
     public Texture2D Crosshair;
 
     private Camera myCamera;
     
     private Transform myTransform;
     
     private Vector3 worldPosition  = new Vector3();
     
     private Vector3 screenPosition  = new Vector3();
     
     private Vector3 cameraRelativePosition = new Vector3();
     
     private float minimumDistanceZ = 30.0f;
     
     private float adjustment = 1;
     private GUIStyle LockonStyle = new GUIStyle();
     private float dist2;
     public Transform enemyship;
     float distance = Mathf.Infinity;
     public GameObject closest;
     
     
     
     
     
     
     // find the closest enemy ----------------start--------------
     GameObject FindClosestEnemy() {
         
         GameObject[] gos;
         gos = GameObject.FindGameObjectsWithTag("lazerhit");   
         Vector3 position = transform.position;
         foreach (GameObject go in gos) {
             Vector3 diff = go.transform.position - position;
             float curDistance = diff.sqrMagnitude;
             if (curDistance < distance) {
                  closest = go;
                 distance = curDistance;
             }
         }
         return closest;
             
         
     }
     
     //-----------------------End-----------------------------------
     
     
     
     
 
     // Update is called once per frame
     void Update () {
         // set enemyship to the closest gameovject with the tag "lazerhit"
         enemyship =FindClosestEnemy().transform;
         
         // GetType distance from player to enemy
      dist2 = Vector3.Distance(enemyship.position, gameObject.transform.position);
         
         //-------------------------------------------
             myTransform = enemyship;
             
             myCamera = Camera.main;
 
                 //Capture whether the player is in front or behind the camera.
         
         cameraRelativePosition = myCamera.transform.InverseTransformPoint(enemyship.transform.position);
         
         
         LockonStyle.normal.background = Crosshair;
         
 
         FindClosestEnemy();
 
     }
     
     
     void OnGUI (){
         if(cameraRelativePosition.z > minimumDistanceZ && dist2 < 400.0f)
         {
         
         worldPosition = new Vector3(myTransform.position.x, myTransform.position.y + adjustment,
                                         myTransform.position.z);    
             
             screenPosition = myCamera.WorldToScreenPoint(worldPosition);
             
             GUI.Label(new Rect(screenPosition.x - 40 / 2,Screen.height - screenPosition.y - 20,40, 40),"",LockonStyle);
             
             }
 
     
 
         
     }
     
     
     
     
     
     
     
     
     
     
     
     
 }