X Windows questions...

1) Is there a call to retrieve the children widgets of a given parent?

2) Can a widget be modified if you're in a callback that was executing by the same widget?

The reason for question 2 is I would like to add children widgets to a particular widget, and I would like to do this from a callback that is currently executing from the widget in question. When I try this, my program core dumps. I can, however, add children to a particular widget if I am in some other callback that was executing from a completely different widget.