Hi Mark,
(I already posted this answer in your other thread, but let's keep THIS thread alive - it makes more sense here in the LabVIEW forum than in Instrument Control forum.)
Since the DAQmx Task is not a native data type that can be passed directly to MATLAB from LAbVIEW, try flattening the DAQmx Task to a string before passing to MATLAB. However, I doubt that you can access the task from within MATLAB, but feel free to give it a try.
Good luck!
- Philip Courtois, Thinkbot Solutions