If you are creating a pulse in software somehow, then you can use Pulse Measurements.vi that's on the Analyze>Waveform Measurements palette. This will require that the input is of the waveform data type with signal and timing information. There's several timing functions on the time & Dialog palette that you could probably use. Check out Tick Count and Elapsed Time. If you could provide more details on what exactly you need to do, we could provide more help.
