Yes, if you have a network card in the desktop. Configure dial-up as
usual, then use Internet Connection Sharing to share the dial-up
connection to the NIC in the desktop.
Then connect the desktop NIC to one of the LAN jacks (not the "Internet"
jack) of the router.
You will have to ensure that the router's LAN IP address is in the
192.168.0.x subnet and you will have to disable the router's DHCP server.