Retroactively disallowing ad hoc networks

I am trying to progrmmatically require the admin password to create ad hoc networks in around 200 Snow Leopard Macs. I have narrowed downt the plist file to /Library/Preferences/SystemConfiguration/preferences.plist

I would love to broadcast a CLI command through ARD or Casper to change the PrefPane > Network > Airport > Advanced button > Require administrator password to: > (check box) Create computer-to-computer networks. I think the appropriate method would be a defaults write command, but I am having a prob developting the appropriate syntax for a <key> within a <dict> within a <dict> within a <dict>.

Can someone give me a hand with this esoteric request?

--Thomas Reed