Only In Range

First of all, I'm using javascript so please try posting only javascript. I'm creating a quest script for my rpg game and have a great quest script but I would like it if you could only see it in a certain range or area. I have many variables in this script so just realize that I have no errors at the moment:

 function OnGUI () {
 
     GUI.contentColor = Color.red;
 
     GUI.Box(Rect(10,10,500,420), questTitle);
     
     GUI.Label(Rect(15,30,500,420), questText);
     
     GUI.Label(Rect(11,410,100,50), npcName);
     
     GUI.Box(Rect(15,100,490,100), "Reward");
     
     GUI.Label(Rect(20,120,490,100), reward);
     
     GUI.contentColor = Color.red;
     
     if (GUI.Button(Rect(400,450,100,30), "Accept")){
         questItem.active = true;
             
     if(autoAccept == false){
         autoAccept = true;
         }
         else{
         autoAccept = false;
     }
 }
 
     if(autoAccept == true){
     GUI.Box(Rect(540,10,150,50), questItems);
     
     GUI.Label(Rect(590,30,100,30), "" + points + "/" + questItemsNeeded);
             
     if (GUI.Button(Rect(300,450,100,30), "Decline")){
     questItem.active = false;
         autoAccept = false;
     }
 }    
 }

Thanks!