I'll have to do some experimenting. But I do know that you can set up a button/key to tell VA to stop listening while that button is pressed. I use TeamSpeak in push-to-talk mode, and use that same button to tell VA to stop listening while I'm talking on TS. Perhaps that functionality can be of use while trying to dictate some voice-to-text entry...
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EDIT: I've also noticed that VA does a lot better job at recognizing commands if you run the Windows speech trainer a few times. Which makes sense, since VA uses the Windows speech recognition software.