creating a main menu

hello everyone!... Im trying to make a main menu with gui textures.What Ive done so far is basicaly add one main gui texture(which is the background) and other textures for each button I want to use in the main menu.I also used a script to change the look of each button when rolling over, but I have 2 problems: first:when I roll over one button, some of them change their look at the same time. second: Im not sure how to add a different link to each one of them separately. I need some help!!.. thanks a lot! This is the script that im using to change the look of the button when rolling over:

var normalTex : Texture2D;
var hoverTex : Texture2D;

function OnMouseEnter(){
    guiTexture.texture = hoverTex;

function OnMouseExit(){
    guiTexture.texture = normalTex;

try this is script :

var NormalTex : Texture2D;
var EnterTex : Texture2D;

function OnMouseEnter()

	guiTexture.texture = EnterTex;
function OnMouseExit()

	guiTexture.texture = NormalTex;

function OnMouseDown(){

Application.LoadLevel(your level);