TerrainGeneration

Hi, this is my first post here in Unity Answers and I'm on here because I am completely stumped I am currently trying to generate some terrain though a script (I am trying to use the TerrainTollkit API) but I keeping getting the same error:

NullReferenceException: Object reference not set to an instance of an object

here is my current script. Its not done I know but I am testing it in a iterative manner to help control errors.

 var voronoiTerrain : GameObject;
 /*
 var randCell : Random.int;
 var randFeature : Random.float;
 var randScale : Random.float;
 var randBlend : Random.float;
 */
 function Start ()
 {
     voronoiTerrain = GameObject.Find("Terrain");
     voronoiTerrain.GetComponent("TerrainToolkit").VoronoiGenerator(FeatureType.Mountains, 32, 0.9, 0.5, 1.0);
 
 }
 function Update () 
 {
     Debug.Log("Test: " + voronoiTerrain.GetComponent("TerrainToolkit"));
 }

A little help would be appreciated because it is bugging the heck out of me...

Oh and I am using Unity 3.4.2