Command Line Software Update Preferences

We just started using a Mac OS X 10.4.8 (PPC) Xserve to act as our in-house software update server. The preference for the location of the software update server is a user-level setting, I've specified this our server in Workgroup Manager.

Since Apple Remote Desktop does not have any kind of built-in "run software update" option, it seems we're going to have to send a Terminal command to the Macs I'd like to test running our software update on. I've found the "softwareupdate" command and if you specify an update to "--install", then it seems to work. However, it's not downloading from our internal software update server, it's going out to the Internet/Apple site. This is happening even if I use the Terminal directly from a logged-in user with the correct preferences. The interesting thing is that if you ask the command line software update to "--list" the updates, only the ones from our server are shown (the location of the server is noted in the text returned). However, when you actually tell it to "--install" then it goes out of our network and downloads from Apple. Running the Software Update System Preferences correctly finds the updates on our server and then downloads them from that server, so it seems to be a command line issue.

Is there a way to specify the location of the software update server in the command itself? The softwareupdate man pages were a bit sparse...

-Doug