Hi Mrinal,
I assume the application you are running is working as expected and the issue you are having is isolated to getting the waveform signal to show up on the output of your DAQ board. Please correct me if I have made a wrong assumption.
In this case I recommend starting with a LabVIEW example such as "Cont Gen Voltage Wfm-Int Clk-Non Regeneration.vi" located in Help>>Find Examples in the Browse according to Task option under Hardware Input and Output>>DAQmx>>Analog Generation>>Voltage. In this case you will want to replace the Basic Function Generator with your code for generating the modulated waveform. Place the contents of your while loop (excluding the loop itself) inside the while loop of the example program.
This should get you started. You may need to adjust the update rate and number of samples you produce to get the timing just right.
Hope this helps,
Jennifer O.
Applications Engineer
National Instruments