Variable value not changing when using OnTriggerStay()

Hey guys,

For some reason my papers variable will not change when I press a key within OnTriggerStay()

The two gameobjects carry out a function, but the variable does not.

      function OnTriggerStay(Col : Collider)
       {
          if(Col.tag == "Player")
          {
              if (Input.GetKeyDown('e'))
              {
                    papers = papers + 1;
                    Debug.Log( "A paper was picked up. Total papers = " + papers );
                    Destroy(gameObject);
                    Destroy(Cassette);
              }
            }
         }
     function Update()
     {
      if(papers == 7){
       Application.LoadLevel("UndergroundCutscene");
      }
     }

I know the variable value stays the same because I used this code to allow me to see the value.

 InvokeRepeating("Paper", 0.1, 0.01);
 
 function Paper () {
         Debug.Log("Papers = " + papers);
     }

Thank you for your time, all answers are greatly appreciated.