HighScore Manage Using PlayerPrefs

I want to manage HighScore levelwise..For that I am using PlayerPrefs plugin.

I have written below code to manage highscore:

ScoreController Script in JS:

 public var highScoreList : List.<int> = new List.<int>();

 function Start () {
     LoadData();
     gameControllerScript = GameObject.Find("Main Camera").GetComponent("GameController");
 }

 function LoadData()
 {
     for (var i : int = 0; i < highScoreList.Count; i++)
     {
         highScoreList[i] = PreviewLabs.PlayerPrefs.GetInt("highScore" + i);
     }
 }

 function Update () {
 if (!once)
     {
         if(GameController.Score >= gameControllerScript.objectiveScore)
         {
                 if(GameController.HighScore < GameController.Score)
             {
                 highScoreList[GameController.level] = GameController.Score; // Error Comes From Here
                 Debug.Log("new high score: " + GameController.Score);
                 SaveData();
             }
                     once = true;
         }
       }
 }
 function SaveData()
 {
     for (var i : int = 0; i < highScoreList.Count; i++)
     {
         PreviewLabs.PlayerPrefs.SetInt("highScore" + i,highScoreList[i]);
     }
     PreviewLabs.PlayerPrefs.Flush();
 }

But it gives me ArgumentOutOf range Exception.. So how do i store and update my highscore for perticuler level?

Consol :

 Argument is out of range.
 Parameter name: index
 System.Collections.Generic.List`1[System.Int32].CheckIndex (Int32 index)
 System.Collections.Generic.List`1[System.Int32].set_Item (Int32 index, Int32 value)

Pleaze Help me..

Thanx for your Support and Help..