I have a problem that I had given up as unsolvable, but after recently
learning about secondary axes, I've made encouraging progress. However,
I'm stuck on the last step(s), and I'm hoping that someone will have
some suggestions.

My organization has been producing reports that contain population
pyramids. In the past, all of their reports have been printed, so it
didn't matter that in order to get the desired look, they had to use
two charts slightly overlapping each other. However, we are getting to
the point where we would like our charts to be available online for
download. If we save the charts from Excel, of course each pyramid has
two charts that become GIFs, which is non-ideal. Here's an example of
what we have now:

http://epdc.org/CPGraphs/HumanCapita...ia_curmale.png
http://epdc.org/CPGraphs/HumanCapita..._curfemale.png

and here is the progress that I've made:

http://epdc.org/junk/HCPsecondary.png

The big remaining problem is that I need (or would really really like)
a single visible y-axis (I'm calling the horizontal axis y because
that's what Excel does). It's not as simple as making one axis
invisible and changing the way that negative numbers are displayed.
Since we would like to keep the age group labels in the middle of the
pyramid, the y-axis would actually need to have two zeros, if that
makes sense.

Any ideas?