Help with array collision script !

I'm making a turn based game were the basic movement is "select a cell and then then move to it". But the player needs to know which "cells" he can move to. To find the "Cell" I made a sphere collider that when colliding with an object with the tag "Cell" it adds it to an array of objects. But i'm stuck on a problem. I need the sphere to remove the "Cell" that stopped colliding with it from the array. Could anyone help me do this? Here's my script:

`

var cellArray = new Array (); var i : int = 1;

function Start (){

}

function OnTriggerEnter (collision : Collider) {

 if (collision.gameObject.tag == "Cell"){
        
        for(var g in cellArray){
        
            i++;
            
        }
            
            cellArray.Push(collision.gameObject);
         Debug.Log("Added " + collision.gameObject + " to list");
         i = 0;
         Debug.Log(cellArray.length);
     
 }

}

function OnTriggerExit(collision : Collider) {

 if(collision.gameObject.tag == "Cell"){
     var h = collision.gameObject;
     for( h in cellArray){
 
         i++;
             
     }
     
         cellArray.RemoveAt(i); 
         Debug.Log("Removed " + collision.gameObject + " from list");
         Debug.Log("Now there are " + cellArray.length + " objects in the array");
         
     
     
 }
 

}