Fading between skyboxes

I’m currently working on a starfox-style game. The idea is for the player to play through all levels without going back to a menu. Thus I want to swap out the skybox and lighting at certain points of the game. I’ve managed to quite simply swap the skybox thus far, but what I really want is to have a smooth fading effect.

My code thus far looks like:

using UnityEngine;
using System.Collections;

public class NewLevel : MonoBehaviour {
	public Material material1;
	public Material material2;
	public float duration = 2.0F;
	private bool newlevel= false;
	void Start() {
	newlevel = false;
	void OnTriggerEnter(Collider other)
		newlevel = true;
	void Update() {
		if (newlevel = false) {
			RenderSettings.skybox= material1;
		if (newlevel = true) {
			float lerp = Mathf.PingPong (Time.time, duration) / duration;
			RenderSettings.skybox.Lerp (material1, material2, lerp);
			Debug.Log ("Skybox should be changing right about now");

The thing is that thus far it does nothing. In fact, as soon as I start the game, the debug message pops up, despite nothing actually colliding with the box. Any suggestions?

Material.Lerp- do not deal with textures. You should write/find shader for that.