Help for MSAA

>From "Gecko Info for Windows Accessibility Vendors"

" When you get a MozillaWindowClass window focused, keep moving to the
first cild if it has a control ID of 0. If it has a contro ID of 1,
find the first ancestor that also has a control ID of 1. This is where
you should start when using MSAA to get the content tree for a Mozilla
application."

Can anyone tell me step by step what to do? I've gotten the hWnd whose
classname is MozillaWindowClass. I did a search to find the child with
control ID of 1 already. But it does not make sense to me to find back
teh ancestor with control ID of 1 cos if I do that, I obviously get
back teh prev parents until the root which all has control ID of 0.

Hence, the AccessibleObjectFromWindow() keeps returning me argument
invalid. :(

Can anyone help me with that? explain to me how to go about doing it.
Thanks alot.