Hi,
The application that you describe is commonly referred to as buffered period measurement. Programming examples featuring this functionality are shipped with NI-DAQ for each development example. For example, in LabVIEW, you can find the example by browsing to: Help>>Search Example>>I/O Interfaces>>Data Acquisition>>Counters. For LabWindows/CVI, these examples can be found by browsing to the cvi/samples/daq/counters folder.
Hope this helps.
Regards,
Erin