Hello Morpheous,
Counters cannot output sine waveforms, so you will need to use analog output for your application. I'm not very familiar with biphasic pulses, but you can use any of the analog output example programs that are included with the NI-DAQ driver as reference for your application. What program are you using (LabVIEW, CVI, C++, .NET, etc.)?
If you are using LabVIEW, you can go to Help >> Find Examples. Once the Example Finder pops up, go to Hardware Input and Output>>DAQmx>>Analog Generation>>Voltage. If you are not using LabVIEW, you can find the examples in the following directory: C:\Program Files\National Instruments\NI-DAQ\Examples.
Hope this helps,
LA