How do I use the ExitCode on the TFS InvokeProcess activity?

In TFS build I call to a nant script using a custom activity InvokeProcess (we use NANT till we will be able to move to "TFS language") I want to f开发者_如何转开发ail the build if NANT fails. I guess I should use the Result property of the InvokeProcess. How I do that? Thanks

I think you can find what you need here.