easy newbie question (I think)

[Brian Clark <bc viz tamu edu>]

How do I access a particular item in a gtk window?
If I have a window, which contains a box, which contains a button, how 
do I access the button, when all I have is a pointer to the window?




I hope that was a clear enough question.  If so, stop reading.   But if 
not...
Here's my example:

I want to gray out a frame which contains a bunch of controls if a 
checkbox is checked.

The checkbox's callback includes a user_data, but that is taken up with 
my class, which has to be passed to the callback, too.  My class can 
contain a pointer to the window (and already contains a pointer to 
another window, which works).  But I don't just want the window, I want 
a specific frame which is in a vbox in another vbox in the window.  
Because the window is large and complicated, I create the window in a 
separate function, so I can't just refer to it directly when getting 
everything started in main.  No matter how I go, I need to access 
something contained in a window, not just the window itself.

I tried:
myClass->window->vbox1->vbox2->myframe
but that doesn't do it.

Thanks for your help.
bc