Your router will not do this for you on it's own.
However, whilst the following method is a little convoluted, it should allow you to share your mobile internet connection through your computer's ethernet port to the router.
First connect your computer to the internet through the mobile device. Now open
Control Panel > Network and Sharing Centre > Change Adapter Settings. Right click on your mobile internet connection and select Properties. Go to the
Sharing tab, check the box to share the internet connection and choose your Local Area Connection from the menu. Now you should be able to share your connection by ethernet to the router or another computer.
You can also share the wifi connection on the computer by opening an Administrator Command Prompt and typing
netsh wlan set hostednetwork mode=allow ssid="Pretty Fly For A Wifi" key=password This will create a hosted network called "Pretty Fly For A Wifi" with the password set as "password" (change this to whatever you want by changing the key in the command above). Now type
netsh wlan start hostednetwork to open the connection. You will have to choose to share your mobile network with this hosted network by going to
Change Adapter Settings again, as described above.
Warning You cannot share a your internet connection with both the Local Area Connection AND the WiFi connection simultaneously. You will have to share with either the ethernet port OR the wifi card - your choice but only the ethernet port will connect to the router.