Tim,
I was unable to find any multi-variable linear regression examples in LabVIEW. I did find the normal linear regression examples, which ship with LabVIEw and can be found in your \examples\Analysis folder. As for multi-variable regression, I did find an applicable HiQ example. HiQ is the free analysis software that ships with LabVIEW. You can install it from your LabVIEW CD, and there is an example called "Multiple Linear Regression" that you can find in your \examples\data fitting folder. It is then possible to interface to HiQ from LabVIEW using the HiQ Script Node in the Mathematics >> Formula subpalette.
I hope this suggestion helps you out. Good luck with your application and have a pleasant day.
Sincerely,
Darren N.
NI Applications Engineer