There are a few options for you to try:
1. Contact the instrument manufacturer to check if they provide LabVIEW drivers for their instruments. If Agilent has VXIplug&play drivers for these instruments, you can then use the "LabVIEW Interface Generator for LabWindows/CVI Instrument Drivers" tool to import the VXIp&p driver into LabVIEW. Please refer to http://www.ni.com/devzone/idnet/development.htm for more information about this tool.
2. Use Instrument I/O Assistant in LabVIEW
3. If you have access to any documentation containing the command set for the instrument, you can try to develop a driver yourself (http://www.ni.com/devzone/idnet/developid.htm)
4. Contact our Alliance Member. Many of our Alliance members have extensive instrument driver development expertise. For a listing of our Alliance Members, go to: http://www.ni.com/alliance.