Can a router be set up without directly connecting to a modem?

[angel]

I know this maybe impossible but our stupid off brand cable provider has the modem locked in the wall. So there's no modem that's easily accessible. Or would I have to buy another modem? Thanks
Additional Details
I can connect to the internet through wired Ethernet connection from wall to computer. But would like wireless for iPads etc.

[Lesus]

You can connect your router to the ethernet connection.

[Mav Maverick]

Yes, take a patch cable and connect from the wall jack to the "Uplink" or similarly labelled port on the back of any WiFi router. (Sometimes it's not labelled but it's a different color). You say you already have internet access via this jacket - that's good. Do not get another modem or something that is described as a "combo modem/wifi router". The modem in the wall is already taking it from the incoming cable coax and putting it on ethernet... now all you need is a wifi ROUTER to get your wireless functionality. By default out of the box, the wireless router should obtain an address from the modem in the wall and be more or less plug and play. Remember to set up a WiFi password to protect your network.