Custom Build Rules
Visual Studio 2010 and 2012 are able to convert custom build rules more or less automatically when you upgrade an existing VS 2008 project. Therefore, since a custom MASM build rule was created for the VS 2008 projects in the c:\Irvine\Examples folder, you can continue to use them in VS 2010 and 2012.

Neither VS 2010 nor VS 2012 contain a Custom Build Rule editor. This is apparently due to the migration to the MSBuild tool. You can read about this issue at the Microsoft Visual C++ Team Blog:

They also discuss some limitations to the conversion process from VS 2008 rules to VS 2010.