encapsulating if statement in update

This will most probably have a stupidly easy explanation but I can't get my head around this, I have a piece of code to create a simple GUI for holding a players level and experience:

 #pragma strict
 
 var currentXP : int = 0;
 var maxXP : int = 500;
 var XPtext : GUIText;
 var Level : int = 1;
 
 function Update () 
 {
     XPtext.text = "Level " + Level + " XP " + currentXP + " / " + maxXP;
     if(currentXP == maxXP)
     
                 //if(Input.GetKeyDown("r")) 
                 //currentXP += 10;
         {
             LevelUpSystem ();
         }
 }
 
 function LevelUpSystem ()
 {
     currentXP = 0;
     maxXP = maxXP + 50;
     Level ++;
 }

I want to know how to incorporate this into the update function properly:

 //if(Input.GetKeyDown("r")) 
 //currentXP += 10;

Thanks!