It is possible to create a new task while the VI is running...and for this you can use the DAQmx Advanced Task Option>> DAQmx Create Task.vi. I don't think you can call DAQ assistant from your VI.
Thanks Kallis, but the task created by "DAQmx Create Task.vi" destroys when LabView exits. I actually wants to give option to user to permanently create a new task during runtime. So, is there any way to launch DAQ Assistant during runtime?