Then you are pretty much out of luck... You need a router with QoS functionality either from a 3rd party firmware or the stock firmware that comes with your router. You really need to control the bandwidth from the router level to be able to limit it effectively.
If your router is compatible with 3rd party firmwares I recommend flashing it with DD-WRT which availiable for free here
From that site you will be able to determine if:
(A) If your router is compatible and which routers are
(B) How to flash the memory of the router with the DD-WRT firmware
If your router is NOT compatible but you still really want to limit bandwidth on your network I recommend purchasing a router that either can be flashed with DD-WRT or buying a router that has stock QoS functionality. I would be weary of buying a router with Stock QoS because it may be limited and not work properly which is notorious for stock firmwares. The DD-WRT's QoS is excellent, I haven't used it myself but I do know other friends who have.
Hope this helps:)
Anymore questions? feel free to ask