Is there a way to define the project file path in a solution using a user macro/environment variable? I can\'t seem to do that.
Kind of like an environment variable is u
MSBuild allows you use to environment variables,
http://msdn.microsoft.com/en-US/library/ms171459(v=VS.80).aspx
So that you should be able to define environment variables as you wish, and then modify vCxproj files to make use of them.
I am not sure if that tip works for sln files, as sln files are not MSBuild scripts.