How can I increase the value of a variable?

Hi, I am trying to make a quicktime event thing when I enter a trigger the E key pops up, and you must press the E key 30 times and then a animation will play. How can I accomplish this? I've tried, but it didn't work. The variable Presses dosen't want to increase.

Here's my script:

 var Ekey : GUITexture;
 var Cube : GameObject;
 var Presses = 00.0;
 var MaxPresses = 30.0;
 
 
 
 
 
 function OnTriggerEnter () {
   Ekey.enabled = true;
  if(Input.GetButtonDown("E")){
  
      if(Presses < MaxPresses){
    Ekey.animation.Play();
    Presses += 1;
    
    if(Presses > MaxPresses){
     Ekey.enabled = false;
     Cube.animation.Play();
    
    
    
       }
    
         }
         
         
        
     }
 
 }
 
 
 
 function OnTriggerExit () {
  if(Presses < 30){
  Presses = 0;
  Ekey.enabled = false;
  }
  else
  
  
  if(Presses == 30){
 
    Presses = 30;
    Ekey.enabled = false;
 
    }
 }