GUI window popup button

how can i put button in place of toogle i want when i click a button a window will popup

 // boolean variable to decide whether to show the window or not.
 // Change this from the in-game GUI, scripting, the inspector or anywhere else to
 // decide whether the window is visible
 var doWindow0 : boolean = true;
 
 // Make the contents of the window.
 function DoWindow0 (windowID : int) {
 
 }
 
 function OnGUI () {
     // Make a toggle button for hiding and showing the window
     doWindow0 =  GUI.Toggle (Rect (10,10,100,20), doWindow0, "Window 0");
     
     // Make sure we only call GUI.Window if doWindow0 is true.
     if (doWindow0)
         GUI.Window (0, Rect (100,20,700,350), DoWindow0, "Window 2");
 }