What is the name that you are invoking your gui under, and how are you invoking it from the command line? Is it "maingui"? The error message you receive is suggestive that you have a created a Callback routine that attempts to invoke the routine "maingui" without providing the "source" and "event" parameters to it. That could happen if your code has
... 'Callback', 'maingui', ...
instead of
... 'Calback', @maingui, ...
