Hello,
I found a few other Developer Exchange posts talking about this hardware...you can search the Developer Exchange for 'Tenney' or for 'Watlow' to find some threads that may help you. I also searched at www.google.com for tenney, watlow, and labview and found a few hits that might be relevant.
If all else fails, you should be able to contact the hardware manufacturer and receive from them a list of applicable commands to send to the instruments.
I hope one of these suggestions helps...also, if you end up developing your own driver, there are some helpful resources for that at www.ni.com/idnet .
Good luck with your application, and have a pleasant day.
Sincerely,
Darren N.
NI Applications Engineer