TG582n Firewall: rule for ssh access to LAN from single IP on WAN

[#1]

Appologies if I missed something in the documentation but can the TG582n router support the following.
Rather than use the "Game and Application Sharing" functionality to open a port to any IP on the WAN, can it be setup to allow access to a port from a range of in-bound IPs?
So this is what I tried already. I defined my own security level in the firewall based on the 'standard' level, then added a rule for ssh access to a server on the LAN from a single IP on the WAN - but here's the thing, it wasn't honoured. Is there something I'm missing?
P.S. I've seen documentation which suggests this is possible in "Expert mode". My understanding is that the TG582n supplied to Plusnet residential customers is that it doesn't have an expert mode. Is it really impossible to do this in "Basic mode"?
Best Regards,
James

[#2]

I'd suggest having a look at nat mapadd using the telnet cli interface. That would appear to let you define a port mapping for a single public IP at least.
You can download the CLI manual from here http://wiki.aaisp.net.uk/index.php/File:TG582n_CLI_Guide_v1.0_public.pdf

[#3]

Hi James,
Most of the commands you'll need are documented in my IPv6 tutorial here. http://community.plus.net/forum/index.php/topic,106578.0.html
You should be able to spot the applicable ones. Let us know how you get on.
Matt