Buffered digital output for NI products using DAQ toolbox?

I would like to do pulse width modulation using a digital output device (NI9401) in order to control the brightness of an LED. I can see the 9401 device from Matlab but unlike with analogue devices, I cannot output a long, arbitrary vector of pulses to it. It seems that I can only set single values at a time which is too slow. Is there some way to do this - either by upgrading to a newer version of Matlab (currently on 2009a) or using the NI DAQmx library?

Note that I do know how to use the digital device as a pulse modulated counter with an arbitrary duty cycle but that doesn't help as I need to change the duty cycle rapidly while the signal is being output.

Thanks

Alex