OnTriggerEnter and Exit using Position Markers? help??

So im trying to make this door open using coliders. i can open it with a button but i need to open it like this:
activate the door using the button, walk into collider and door will open automatically.

im new to unity and dont understand what im doing wrong, can someone help!

using UnityEngine;
using System.Collections;

public class AutobotDoor : MonoBehaviour 
{
	//Components
	Animator doorAnim;
	//Refrences
	public GameObject lightObj;
	Light light;
	Renderer lightRend;
	public Transform platform;
	public Transform[] posArr;
	public int targetPos;
	public float speed = 5f;

	void Start () 
	{
		//Get Component
		doorAnim = this.GetComponent<Animator>(); 
	}
	
		void OnTriggerEnter(Collider otherCol)
		{
		//check if the player emetered the trigger
		if(otherCol.tag == "Player")
		{
			//DoStuff
			platform.position = Vector3.MoveTowards(platform.position, posArr[targetPos].position, speed * Time.deltaTime);("DoorState" , true);
		}

		}	

		void OnTriggerExit(Collider otherCol)
		{
		//check if the player emetered the trigger
		if(otherCol.tag == "Player")
		{
			//DoStuff
			platform.position = Vector3.MoveTowards(platform.position, posArr[targetPos].position, speed * Time.deltaTime);("DoorState" , false);
		}

		}
x
		void OpenDoor()
		{
			// 1) Check current state of targetPos and change it
			if(targetPos == 0)
			targetPos = 1;
			else
			targetPos = 0;
		}

	void Update () 
	{
	
	}
}

here is wat it looks like. i just cant get it right