Mini as wireless router without Internet connection

Hi,

Is it possible to setup my Mini as a wireless router without an Internet connection? The Mini would not have access to the Internet. Other computers could, however, connect to it through Wifi and they would be in the same network as the Mini. The network sharing option seems to require an Internet connection.

Thanks

I see that people use Airport, but I don't have the Airport dongle. It it necessary to use Airport? I don't see Airport as an option in the "using" selection.