External trigger for NI 9233 in Data Acquisition Toolbox

I have an NI USB-9233 unit, and am running R2012B with the Data Acquisition Toolbox. I want to set up a session where data acquisition is triggered at a defined voltage level on the input to channel ai0 of the unit. I create a session and add an analog input channel. I then try to set up the trigger with the command...

       s.addTriggerConnection('External','Dev1/ai0','StartTrigger').

Then I get an error message, "'Dev1' does not have any terminals that can be used for synchronization and clocking."

Can anyone tell me how I can set up this simple triggering?

Thanks, Bill

FORGET MY QUESTION. After looking into the Session Based documentation a little more, I have come to realize that the Mathworks has come up with another brain-dead version of the Data Acquisition Toolbox, as least as far as I am concerned. After waiting years for the Mathworks to add the capability to deal with IEPE input, they have finally done that with the session-based facility. However, at the same time they completely eliminated the analog triggering capabilities of the "legacy" version. The utter stupidity of the people in charge of the DAQ toolbox at the Mathworks is simply amazing!