Begin a 2D GUI block inside the 3D handle GUI.

	// Create a 180 degrees wire arc with a ScaleValueHandle attached to the disc
	// that lets you modify the "shieldArea" var in the WireArcExample.js, also
	// lets you visualize some info of the transform and finally lets you 
	// reset the shield area value to 5 by clicking on a button
	
	@CustomEditor (DummyButtonScript)
	class GUIButtonHandle extends Editor {
	    function OnSceneGUI () {
	    	Handles.color = Color.blue;
	 		Handles.Label(target.transform.position + Vector3.up*2,
	 				target.transform.position.ToString() + "\nShieldArea: " +
	 				target.shieldArea.ToString());
	 		Handles.BeginGUI(Rect(Screen.width - 100, Screen.height - 80, 90,50));
	 		if(GUILayout.Button("Reset Area"))
	 			target.shieldArea = 5;
	 		Handles.EndGUI();
	 		
	        Handles.DrawWireArc(target.transform.position, 
	        		target.transform.up, 
	        		-target.transform.right, 
	        		180, 
	        		target.shieldArea);
	        target.shieldArea = 
			Handles.ScaleValueHandle(target.shieldArea,
        					target.transform.position + target.transform.forward*target.shieldArea,
	        				target.transform.rotation,
	        				1,
	        				Handles.ConeCap,
	        				1);
	    }
	}

	// DummyButtonScript.js
	
	var shieldArea : float = 5;