how to instantiate GUI Texture

I’m trying to instantiate a GUITexture only once, and only if the player is in the trigger box that i made. However when i instantiate with the following script it keeps making copies since im in the trigger constantly. How do i instantiate my guitexture once?
script:
var doorUp : AnimationClip;
var openDoorText : GUITexture;

function OnTriggerStay (mytrigger : Collider) {

if(mytrigger.gameObject.name == “player” )
{

door = gameObject.Find("door");
var instance : GUITexture = Instantiate(openDoorText, transform.position, Quaternion.identity);

if(Input.GetButton(“openDoor”))

	door.animation.Play("hoistDoorUp");
}

}

Why not use OnTriggerEnter? This is called only once you enter the collider.

function OnTriggerEnter (mytrigger : Collider) 
{

  if(mytrigger.gameObject.name == "player" ) 
  {
     door = gameObject.Find("door");
     var instance : GUITexture = Instantiate(openDoorText, transform.position, Quaternion.identity);

     if(Input.GetButton("openDoor"))
       door.animation.Play("hoistDoorUp");
   }
 }