What makes running the coax line for your cable modem not possible in that room? Cable company's have rules their employees have to follow. When I was installing cable we where not allowed to wall fish cable at all. We could only run it from outside and then drill straight in or in some cases we could run it though a crawl space and angle drill from above. This is for single family homes only. For apartments of more than 4 units we could not run any outlets at all.
If you are in a house and the cable company can not run the outlet for you then you could still have it done by a custom wiring contractor that has less restrictions on what they can do. It will cost allot more though. If you go this route I would have them just run an ethernet cable from the room you have the modem in to the room you need the connection in. Reason being a custom contractor will not know if the signal is strong enough on the coax for the modem when they are finished because they lack a signal meter. Ethernet will work for as long a run as you will likely need unless you live in a stadium.
If you are in a house and the cable company can not run the outlet for you then you could still have it done by a custom wiring contractor that has less restrictions on what they can do. It will cost allot more though. If you go this route I would have them just run an ethernet cable from the room you have the modem in to the room you need the connection in. Reason being a custom contractor will not know if the signal is strong enough on the coax for the modem when they are finished because they lack a signal meter. Ethernet will work for as long a run as you will likely need unless you live in a stadium.