Just enabled ICS on the internet connection and share it w/ the other network connection (the one leading to the router). In fact, since ICS provides a router of its own, you don't actually need the routing features of the router (WAN). It will still work, but now those users are behind two firewalls, double NAT’d, etc., which complicates firewall management for remote access purposes (if that’s a requirement). Instead, you could just assign the router a static IP address of 192.168.0.99, disable its DHCP server, and connect them LAN to LAN. So now it's nothing more than a switch (and of course, if it's a wireless router, it remains a wireless AP).