I am using VS 2010 Ultimate on Windows 7 Home Premium x64. I originally wanted my post build event to run on a successful build AND release configuration. In other words, skip the post-build event for Debug. That isn't possible in a straighforward fashion.

As it turns out (apparently) the post-build event is written to a batch file that is subsequently executed. That being said I tried to do the following in the Post-Build event:

if "$(ConfigurationName)" == "Release" (
      SET EXE="N:\My.Net\Tools\SolutionPostProcessor.exe"
      ECHO %EXE%
      %EXE% <list of command line parameters built with VS macros
)

Now, when I set my configuration to Release I see only the following:

    WebApplication -> drive:/path/to/webapplication.dll
    ECHO IS ON 

And that is it, the %EXE% execution is skipped totally as if there was nothing on that line. If on the other hand I replace that with the lengthy path to the executable plus its command-line parameters, then it is executed. Apparently VS.2010 post build events is ignoring user-set variables (btw it is NOT an environment variable)