Hello:
LabVIEW 7.0 should have an example that will work for you. Launch the NI Example Finder by selecting "Help >> Find Examples." From there, navigate to the "Hardware Input and Output >> Traditional DAQ >> Digital Input and Output >> E-Series" and select the VI named "Write to 1 Dig Port.vi." This VI will do exactly what you want.
If you do not have those examples, then you need to reinstall NI-DAQ 7.1 (can be found on www.ni.com/support) and that should install those example files.
Good Luck!
Sincerely,
Brooks B
Applications Engineer
National Instruments