I have a problem with my prefab. I import my model and created a prefab "Player". Again i did the same step to the "Enemy", but i need check the distance of player with enemy and when i use

Vector3 D = player.position - tranform.position(script attached in enemy)

it check the prefab position and not the gameObject in scene. Then i use it

Player = GameObject.FindWithTag("Player").transform;

and work with player.... but my "Enemy" is several equal in scene, and i not instantiate them. It is fixed before. They have a function that does count in a variable "Player" and one bool variable. Basically when comes to near of enemy, it count a alert, and enable a GUI placed on player script.

What i need? I need a solution for them to function independent.

Here my enemy script.

using UnityEngine;

public class CDA_01 : MonoBehaviour {

#region Status
private enum NPCStates
{
    Searching,
    Walking,
    InAlert
}
private NPCStates state = NPCStates.Searching;
#endregion

private Transform enemy;    

MyPerson scriptPlayer;

public void Start()
{
    scriptPlayer = GameObject.FindWithTag("Player").GetComponent<MyPerson>();
    enemy = GameObject.FindWithTag("Player").transform;

}

public void Update()
{
    if (state == NPCStates.Searching)
    {
        //Standing
        animation.Play("Standing");
        SearchingPlayer();

    }

}

private void SearchingPlayer()
{
    Vector3 D = enemy.position - transform.position;

    if (D.magnitude <= 8)
    {
        **//HERE IS THE PROBLEM**
        scriptPlayer.nearToCDA = true;
        scriptPlayer.countAlert += 0.4f;
    }
    else
    {
        scriptPlayer.nearToCDA = false;
    }


}

}

Here part of player script

 using UnityEngine;
 using System;

[RequireComponent(typeof(CharacterController))]

public class MyPerson : MonoBehaviour {

public float countAlert = 0;
public bool nearToCDA = false;

........   

**//HERE THE PROBLEM**
public void OnGUI()
{
    if (nearToCDA)
    {
        GUI.Box(new Rect(Screen.width / 2 - 80, Screen.height / 2 + 150, countAlert * 2, 20), "");
    }
}

}