I would agree with you but he's not talking about webaccess, he's trying to get NAS Navigator to see it. That will never work without both the computer and the NAS being on the same IP subnet. The only way to accomplish this would be to set up a VPN.
I haven't used a commercial VPN but I'm pretty sure that won't work for this. It needs to be a VPN set up at the site, in this case the house. If your router has VPN functionality you can use that, otherwise you'll need something to be a VPN server at the house.
Alternatively, you could use webaccess if you just want to be able to access a specific share/shares remotely.