There are daq counter examples for LabVIEW that demonstrate how to count rising-edges of TTL pulses. You can access the examples through the help menu in LabVIEW. For the PCI-1200 you will want to view the data acquistion counter examples for 8253-based devices. Check out the Event Counting example.
Raecine Meza National Instruments http://www.ni.com/ask