Thanks Deborah It's good to know that the code does work. Mine gives the following error when I go straight into the channel property :
code -200088 Property Node DAQmx Channel (arg 1) in add_units[1].vi <append> Encouraged by your success I'm going to go back into the MAX explorer and check through my channel set up to see if that's where my problem is. Thanks again for your help, I'll let you know how I get on. Ian
