I looked on the Instrument Driver Network(www.ni.com/idnet) and found LabVIEW instrument drivers for the HP 6633 and 6623. I don't know how familiar you are with instrument drivers but using the high level functions in them eliminate the need for you to mess around with the low level commands.
Here are links to the driver: 6623 http://zone.ni.com/idnet97.nsf/9b2b33e1993d877786256436006ec498/a0c4368e36f07164862568aa0077e162?OpenDocument
Both of the drivers are IVI (www.ni.com/ivi/) compliant. When you visit the links above to the drivers please take a look at the required software. You'll need to have VISA (usually installed with LabVIEW) a nd the IVI engine. Both can be downloaded for free.