intra widget event grabs?

[robert crowther <zen95156 zen co uk>]

I'd like to catch an event on one widget,

a mouse button press,

then catch the same mouse button releasing -

but know which widget it released over

(kind of like a drag, but from one widget to
another).

But I don't know much about events at all. What
I do know is that once you use a button press
handler, the release seems to associate
with the same widget as the press (wherever the user
mouse pointer wanders on the screen).

Naievely, I tried a grab release, but it seems to have
no effect, and there doesn't seem to be a grab anyway.

Anyone know what goes on here? Is the above possible?

Cheers

Rob