How can I use relative path names in Doygen config, or use enviroment variables?

Question

Assume I have a directory structure like this

~j/p1/src/
         /Doxyfile1
         /ss1/
             /f1.c
             /f2.c

~j/p2/src/
         /Doxyfile1
         /ss1/
             /f1.c
             /f2.c

The contents of ~j/p1 and the contents of ~j/p2 were created as workspaces for the same part of a single Subversion repository.

I'd like the file list of the html docs produced by Doxygen to omit the "~j/p[12]/src", without changing the contents of either Doxyfile1.

To this point, I've had to modify my Doxygen configuration files to specify the absolute pathnames for at least some of the filenames or working directories used by Doxygen. I've searched the Doxygen documentation, read stackoverflow, and done a few Google searches, but I can't find a way to specify either relative path names or to use environment variables to eliminate this need. Is there a way to make the Doxygen configuration file "file system position independent?"

Thank you. Jim