Drag operation swallows mouse events?

[T]

Does anyone know how to get mouse click events while the mouse is in
the middle of a drag operation?

There are several areas in the app where a particular item may be
dropped on to. When the user drags this item over each, I would like
it to become "highlighted" (color change).

I am able to know when to enable highlighting because the
TransferHandler gets activated when the dragged object enters the drop
accepting region, but I can't figure out any way to know how to turn
the highlighting off.

Is there some global way to know that the mouse has been released?
This is becoming a huge time sink.

Thanks for any help!
Ted