Hi Jingli,
In this discussion thread I already described, how to acquire data from a DAQ board:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=50650000000800000069E70000&UCATEGORY_0=_317_&UCATEGORY_S=0
For output it's almost the same.
This time the virtual channels in MAX have to be analog output channels.
Instead of using the NI-DAQ input block in DIAdem you have to use the NI-DAQ output block.
Just one more caveat: DIAdem cannot do hardware output using hardware clock, so you have to do this in software clock.
Richard H.
National Instruments