Line erase Using Line Renderer

Hi i am new to this unity., i am writing a script which draws a line wherever the mouse position is,,,., but i want to erase the previous lines drawn..,!! using arrays.,.,!!! Its urgent., please help me out.,., here is my code,.,`var startWidth = 0.0005;

var endWidth = 0.0005;

//var aMaterial : Material;

var Line1Trace= new Array(20);

var line : LineRenderer;

var index:int=0;

var c1:Color;

var c2:Color;

var ppp = new Vector3();

var i:int;

function Start ()

{

line = this.gameObject.AddComponent(LineRenderer);

line.SetWidth(startWidth, endWidth);

line.SetColors(c1,c2);

// line.material = aMaterial;

line.useWorldSpace = true;

line.renderer.enabled = true;       

}

function Update()

{

var ray = Camera.main.ScreenPointToRay ( Input.mousePosition );

line.SetVertexCount( index + 1 );

Line1Trace.push(ray.origin);

ppp = Line1Trace.pop();

line.SetPosition( index, ppp );

index++;

Debug.Log( "Ray Origin " + ray.origin);

}

`