IP networks and net masks

[Tim Wunder]

I'm currently using a freesco router to access the internet. Currnetly, 
I have no controls on it for local access out to the internet. So my 
son's PC accesses the internet by using the router as the gateway. Now, 
I'd like to be able to allow only 192.168.1.2 (my PC/server) to be able 
to access the internet through my router, and to run squid and 
squid-guard (or dans guardian) on my server to control internet access.

Now, freesco allows me to add IP addresses to /etc/banlist.cfg. I can 
ban a single IP address by adding the line "l,192.168.1.5", or a network 
by adding "l,192.168.1.0/24". Can I use a netmask other than /24 that 
would only allow 192.168.1.2 access to the 'net thru the router?

Any other ideas for a means of controlling 'net access?

Thanks,
Tim