signal/event for focus leaving a container

[Paisa Seeluangsawat <ps0087 unt edu>]

Hi,

I'm creating a form and want to prevent the user from focusing out of
the form until certain conditions are met.

Is there a signal or event associated with a container that emit when
keyboard focus move from inside the container to outside?

I tried "focus" signal, and "event" with GDK_ALL_EVENTS_MASK, but
still no luck.  Don't parent widgets get a cascaded
focus-[in/out]-event along the widget tree?

Thanks,

Paisa