Whats wrong with this ladder climb script?

I'm trying to make a script that the GUI (with a hint) becomes visible when enter collider. And when the player is IN the collider + he presses Z the animation climb ladder needs to play. My script:

 #pragma strict
 
 var IsInTrigger : boolean = false;
 
 function Start () {
     guiText.enabled = false;
     }
 
 function OnTriggerEnter(other: Collider){
     if (other.tag == "Player"){ // remember to tag the player as "Player"
     guiText.enabled = true;
     IsInTrigger = true;
     }
 }
 
 function OnTriggerLeave(other: Collider){
     if(other.tag == "Player"){ 
     guiText.enabled = false;
     IsInTrigger = false;
     }
 }
     
 if(IsInTrigger == true && Input.GetKeyUp(KeyCode.Z)){
     animation.Play("ClimbLadder");
     IsInTrigger = false;
     guiText.enabled = false;
     }