title: Use a "User Macro" in .vcproj RelativePath
body: <p>Inside <a href="http://msdn.microsoft.com/en-us/library/2208a1f2.aspx" rel="nofollow noreferrer">.vcproj files</a> There is a list of all source files in your project.</p>
  
  <p>How can we use a macro to specify the path to a source file?
  If we do this:</p>
  
  <pre><code>&lt;File
     RelativePath="$(Lib3rdParty)\Qt\qtwinmigrate-2.5-commercial\src\qmfcapp.cpp"&gt;
  &lt;/File&gt;
  </code></pre>
  
  <p>The compiler cannot find the folder:</p>
  
  <pre><code>qmfcapp.cpp
  c1xx : fatal error C1083: Cannot open source file: '.\$(lib3rdparty)\qt\qtwinmigrate- 2.5-commercial\src\qmfcapp.cpp': No such file or directory
  </code></pre>
  
  <p>As you can see, our project compiles in several source files from QT. QT lives inside a folder of external libraries, and we don't want hardcode the path from our project to that folder (we have a very large solution)</p>