how can i do this!!!!??

can any one help me … what does this mean???..how can i do that???

//again, cube is a varible defined elsewhere …is it like though a Var:GameObject?

You cannot destroy a cube with the press of a GUI button?

Then I will conclude that you are pretty new to Unity. Amirite?

I would recommend you watching some tutorials just to get you started.

TornadoTwins

And this:

GUI´s

When you are done watching all of hes tutorials you will properly more or less have all the basic skills needed to destroy a cube with a GUI button.

You can also(if you do not want to watch the tutorials) take a look at the destroy function.

Destroy

Maybe this as well

Transforms

Although I don’t know if it has to be a GameObject, or some other variable type, what you have to do is to define a variable named Cube at the top of your script like this

var Cube : GameObject;

And then you can drag and drop the cube from the inspector view of that script to assign a value to the variable.

PD: I assumed that you were doing it in JavaScript

Yes you define GameObjects via variables. If you only have one cube you pre-define it as this:

var myCube : GameObject;
function Update () {}

Or you could do this at runtime with something like (never do finding in Update due to performance):

function theFunction () {
    var myCube = GameObject.Find("TheNameOfYourCube");
}

To access objects from other scripts you use:

theObject.GetComponent(TheThingYouWantToAccess).theStuffInsideTheThing

Good reading:

GameObject.Find

GameObject.GetComponent

Accessing other objects

Defining variables