Hi Eric,
Data Acquisition Toolbox MATLAB R2012a prerelease has added new function for triggers and clocks . If you have a valid license you can download the prerelease here You would need to use
function to provide your device with an external clock.
You can modify the below code to suit your requirements:
s = daq.createSession('ni');
s.addAnalogInputChannel('Dev4', 0, 'Voltage');
The below command will add a external scan clock connection from an external source to the PFI0 terminal on Dev4. Make sure you connect your external clock to PFI0 physically
s.addClockConnection('External','Dev4/PFI0','ScanClock');
Your acquisition will now use your external clock
Hope that helps,
Manisha