I think this is similar to a question I asked earlier, which was "Why can't a secondary data connection be both submit and receive?"
I wrote a web service that takes an Infopath Group as it's input (I'm passing the parameter to the data connection with: Include XML subtree & Submit data as string).
I created the data connection as Submit so that I could specify the InfoPath Group.
I also want this web service to return a value back to InfoPath.
How can I do that?