http://blogs.msdn.com/b/visualstudio/archive/2010/05/26/programmatically-adding-removing-querying-vc-build-customizations.aspxBuild Customizations (Custom Build Rules in earlier editions) are commonly used for invoking external tools that translate files from one format to the other, often resulting in C++ sources that can be compiled at the C++ compilation step. In this posten-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)http://blogs.msdn.com/b/visualstudio/archive/2010/05/26/programmatically-adding-removing-querying-vc-build-customizations.aspx#10052960Sun, 22 Aug 2010 20:52:06 GMT91d46819-8472-40ad-a661-2c78acb4018c:10052960Tomasz Grobelny<p>If you pass full path to LoadToolFile everything works fine. However, if you want to add BC located in a path referenced by custom msbuild variable (like $(CustomMsBuildVariable)\BC.targets) then only .targets file is added (even if .props file is in the same location). Looks like a bug in VS2010.</p> <div style="clear:both;"></div><img src="http://blogs.msdn.com/aggbug.aspx?PostID=10052960" width="1" height="1">