Ether's Post was a lifesaver for holonomic drive(partly because it is so easy to make sense of.) I whipped this up after reading it. All you need to do is plug in your joystick dev ref to the one side, and then plug the 4 values that output on the right into your 4 drive VI's.
Download it here:
http://files.me.com/eovnu87435ds/k0i3pn
(Link expires March 19, 2010)
Note, I did not test this yet, since we didn't get our mechanum wheels yet
hope this helps, and of course, all credit goes to Ether