Reacting to MOUSE_MOVE outside app's boundaries

I’m finding that when adding a MOUSE_MOVE event handler at the root level of a script in the mxml file that mouse events aren’t generated when the mouse is moved outside the application area, even if the flash app still has the focus.

For example, a custom vertical scroll bar. Dragging the scroll bar is fine, but a small horizontal shift of the mouse, taking the cursor outside the flash app’s boundaries, will cease movement until the mouse is brought back in.

It doesn’t appear to work this way when adding the MOUSE_MOVE event to the Stage when I tried it in Flash CS3.

Should I be prefixing the addEventListener with a different object?