<Target Name="CustomBuildStep"
          Condition="'@(CustomBuildStep)' != '' and '$(SelectedFiles)'==''"
          Inputs="%(CustomBuildStep.Inputs);$(ProjectFileName)"
          Outputs="%(CustomBuildStep.Outputs)"
          DependsOnTargets="ComputeCustomBuildOutput"
          BeforeTargets="$(CustomBuildBeforeTargets)"
          AfterTargets="$(CustomBuildAfterTargets)"
   >

   </Target>