Unless you can get an additional IP address from Rogers, it can't easily be overcomed. if they expect the PC to be the only one connected to the modem. Does Belarc run whenever a connection is established with the office or do you run it only once and send the results? I presume that the connection is through a VPN connection and if so, why would they care?
Is that PC connected to a router via Ethernet? Do they allow NAT as long as Ethernet is used or do they absolutely require a valid Internet address?