Setting up collider sensor to test if user enter from a single direction

The easier solution will be creating two colliders. the first collider sense the player and tell the second collider the direction is sensed.

the first collider code:

using UnityEngine;
using System.Collections;

public class mistake4Collider : MonoBehaviour {

    public static bool collidedA;
    void OnTriggerEnter(Collider other){
        if (other.gameObject.CompareTag ("Player")) {
            collidedA = true;
        } else {
            collidedA = false;
        }
    }
}

for second collider

using UnityEngine;
using System.Collections;

public class mistake4BCollider : MonoBehaviour {

    bool ToggleGUI = false;
    bool isCreated = false;
    GameObject msg;

    void OnTriggerEnter(Collider other){
        if (other.gameObject.CompareTag ("Player")) {

            if (mistake4Collider.collidedA == true){
                ToggleGUI = true;
                playerLives.lives -= 1;

            }
        } 
    }

    void OnGUI(){
        if (ToggleGUI == true) {
            if(!isCreated){
                GameObject msg = (GameObject)Instantiate(Resources.Load("GUI/Mistake4"));
                isCreated = true;
            }
        }

    }
}