Change material per element

I have made a car in 3ds Max with about 11 different materials.
I want to change most of the materials in code. But I can only get to changte “Element 0”.
I’d like to be able to change (for example) “Element 4” as wel.
How can I make this work???

With this code I’m able to change “Element 0” by clicking 3 different buttons. Every button changes the material of “Element 0” to another material.

var Car : GameObject;
var CarPaint1 : Material;
var CarPaint2 : Material;
var CarPaint3 : Material;

function OnGUI()
{
	if(GUI.Button(Rect(0,0,100,50),"Blauw"))
	{
		Car.renderer.material = CarPaint1;
	}
	if(GUI.Button(Rect(0,50,100,50),"Oranje"))
	{
		Car.renderer.material = CarPaint2;
	}
	if(GUI.Button(Rect(0,100,100,50),"Zwart"))
	{
		Car.renderer.material = CarPaint3;
	}
}

You need to be using Car.renderer.materials which is an array of the materials.