Block a specific computer on my home network?

Networking has never really been my strong suite, but... is it possible to block a specific IP on my home network at specific times -- say, allow access all day, then shut off at night?
What I want to do is block Internet access on a laptop and an iPod Touch during the night, while still allowing all the other computers access.
The set up is this:
Modem/Internet provider: HughesNet (It's sattelite, if that chances anything)
Router: Linksys (I can't think of the exact model right now)
And the modem/router are attached to a desktop running Windows XP. The computer I want to block has Windows Vista, and I wanted to block an iPod Touch, too.

Also, how can I get the IP Address for the iPod?
Posted via Mobile Device

You'll first need to look at the Linksys router and get the model number, not all of them support access filtering. I suppose you can skip trying to find the model number if you can login directly to the router setup page:

http://192.168.1.1

Username: admin
Password: admin

Try opening that URL with the username / password, it should be the default IP address to the Linksys Router. Let me know if it works or doesn't work and we'll go from there, it's very simple once you're logged in. :)