Flex :: MouseUp And MouseMove Outside Of The Application?

I'm trying to implement a very simple way to select a subsection of the screen via mouse. The workflow is the standard one for many apps - click on starting point, move mouse and transparent rectangle updates between first point clicked and current position of the mouse. The basic code looks something like this (minus the graphics, which is simple)

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"

[Code].....

This breaks down when the user moves the mouse outside of the app. Not only _currentPoint stops updating, but also if you let go the mouse button outside of the app you miss the mouseUp event, i.e. when you move the mouse back on the app _currentPoint starts updating again as if you had never let go of the mouse button. Was wondering if there is a way in Flex (for web apps) to get around this by listening to mouseMove and mouseUp events when outside of the app (if that's possible)