wx.Sizer proportional behavour

[Mark Erbaugh]

I've designed a frame with three panel's.  The frame is constructed with
a vertical box sizer.  The top component of the vertical box sizer is a
horizontal box sizer. The first two panels are the two components of the
horizontal box sizer. The third panel is the bottom component of the
vertical sizer. This is illustrated below with panels as A, B and C

AAAAAAA|BBB
AAAAAAA|BBB
-------+---
CCCCCCCCCCC
CCCCCCCCCCC

I would like the top left panel (A) to expand as needed to make the
width of the top two panels equal to the width of the bottom panel (C).
I'm adding panels A and B to the horizontal box sizer:

Add(A, 1)
Add(B, 0)

However, when the frame is displayed, the extra space is being added to
panel B.

What am I missing?

Thanks,
Mark