how to determine relocated package location during %post phase

[Norm Bagley <nbagley lextel com>]

I have set up an rpm package to support install relocation using Prefix:. 
During the %post phase, I want to run an executable that is installed with 
the package, and it's first argument is the filename of another file that 
is installed with the package. In other words, the package contains an 
executable that post-processes one of the installed files. Can I do this 
while supporting re-location? How? Thanks.