Hi JCP,
I personally have not used LabVIEW with the Kestrel 4000, but I did want to let you know that you can request a driver through the National Instruments Instrument Driver Network. Just go to www.ni.com/idnet and click the link for "Request Drivers." If there are enough requests for a certain instrument, then a driver may be made. Hopefully someone else on this message board may also have some experience with the Kestrel device.
John M
National Instruments