command line options to php.exe

I'm trying to pass command line options to php.exe under IIS 5 (win2k), but without any success. What's going on is that I've got two sites that need their own include_path's. I've tried putting "C:\php\php.exe -d include_path='.;c:\foo' %s %s" and "C:\php\php.exe -c c:\foo %s %s" into the IIS configuration for each site, but neither has had any effect. Is what I'm trying to do possible? Thanks very much for your time. Peter Witkop