Handling postun scripts in Upgrade scenario with spec files

[Kala B <kalabalun gmail com>]

Hi,
I have a spec file, where in %post I add my library path to
/etc/ld.so.conf. When I uninstall the package, I remove the same from
/etc/ld.so.conf.
Now when I have a newer version of my code, my users could either
install just the newer version or upgrade from the older version.
When users upgrade, an install of the newer rpm works fine ( adds to
/etc/ld.so.conf ) and then uninstall of the older version removes the
just added path from  /etc/ld.so.conf.

Does rpm spec file give me help to handle such situations? 
Any idea on how this scenario must be handled?

Thanks a lot!
Regards
Kala B