I'm not sure on how to connect a router system to do the following and need advice 
. We have 3 computers here now, currently only this one is online, but we intend to get them all connected. We will need to use wireless connection for the new ones to connect, but we want this machine to remain hard wired for security issues. This machine connects using a USB modem. If possible, the best arrangement would be that the other machines can connect wirelessly without this one needing to be on. It is important that this machine does not transmit on the wireless system however. We do not currently own a router so that can be decided on once a system has been worked out. Any help much appreciated, I can draw some kind of diagram if it helps; that turned out to be quite confusing when I read it back.
. We have 3 computers here now, currently only this one is online, but we intend to get them all connected. We will need to use wireless connection for the new ones to connect, but we want this machine to remain hard wired for security issues. This machine connects using a USB modem. If possible, the best arrangement would be that the other machines can connect wirelessly without this one needing to be on. It is important that this machine does not transmit on the wireless system however. We do not currently own a router so that can be decided on once a system has been worked out. Any help much appreciated, I can draw some kind of diagram if it helps; that turned out to be quite confusing when I read it back.