show another gui menu

newbie need help... how to show another gui menu when click gui button..?

 var GUIEnabled : boolean = false;
   function Update()
     {
         if(Input.GetKeyDown(KeyCode.Q))
         {
     GUIEnabled = !GUIEnabled;
     }
          function OnGUI ()
             {
             GUI.skin = MenuSkin;
             if (GUIEnabled){
              var groupWidth = 250;
             var groupHeight = 280;
             var x = ( Screen.width - groupWidth ) / 2.0;
             var y = ( Screen.height - groupHeight ) / 2.0;
                  GUI.BeginGroup( Rect(x,y,groupWidth,groupHeight) );
         GUI.Box( Rect(0,0,250,200 ),"Menu List :");
          if(GUI.Button (Rect (40,40,180,40), "floor 2")){
                   transform.position = SpawnPoint.position;
             }
           if(GUI.Button (Rect( 40,83,180,40),"option")){
               ........................    
                    
              }
      
                  GUI.EndGroup ();
                  }  
            
         }
 
 

how to show another gui box when i press Button "Option" and hide active gui ??