Anna,
Sorry for the follow up, after reading your question again, there may be a better solution to what you are trying to do. If what you want to do is control a VI you may be better off using VI Server ... if you go the the Resource Library in NI Developer Zone: http://zone.ni.com/libraries/ and follow LabVIEW to LabVIEW>Connectivity>VI Server you should find a few examples that may prove useful. There are also some VI server examples that ship with LabVIEW that you can use.
Many examples refer to accessing a VI on your own system however by setting up the preferences correctly you can give access to other machines so they can control VIs on the server.
With VI Server you won't have to worry about defining your own interface and parse commands etc. You
can simply create a VI that performs the function you're interested in and then call it remotely ... one example that sounded interested was titled "VI Server and Semaphores over a Network". I haven't tried to run it but the description seemed like it may be what you need.
Kamran