Adding commands to buttons?

I'm trying to add commands to the buttons of my game. I want that when the button is clicked to open a new scene, I'm trying to do this much longer I can not, already tried here in the community but also found nothing to help me. I am using this script:

 / * Example level loader * /
 
     // JavaScript
     OnGUI function () {
     // Make the background box
     GUI.Box (Rect (10,10,100,90), "Loader Menu");
     // Make the first button. If it is pressed, Application.Loadlevel (1) will be executed
     if (GUI.Button (Rect (20,40,80,20), "Level 1")) {
         Application.LoadLevel (1);
     }
 
     // Make the second button.
     if (GUI.Button (Rect (20,70,80,20), "Level 2")) {
         Application.LoadLevel (2);
     }
 
     GUI.EndGroup ();
 
 }

I do not know if there's anything wrong with it, I know I have to write the command in more if I tried several ways and nothing happens when testo in the game, ie the scene does not open. I tried also to use those scripts that are in the tutorials of unity http://unity3d.com/support/documentation/ScriptReference/GUI.Button.html more when I try to use these scripts to read and unity does not say to a semicolon at the end please explain me also how close these right script to work. thank you