The product documentation and the blog post TFS Integration Platform – @@MISSINGFIELD@@: Question & Answer 16 both document the it is possible and valid to use the special token @@MISSINGFIELD@@ more than once in the configuration as shown in the following configuration extract:

When creating such a configuration, however, the TFS Integration shell and the MigrationConsole both report the error “Business rule evaluation of no multiple WIT source fields mapped in MappedField: Failed”.

This has been identified as an issue in the tool for builds ranging from May 2010 to March 2011 and will be addressed in the next builds of the product. Please contact me if you need this feature urgently in the meantime.