Your mobo might have some fan headers on it. They are usually small 3 pin connectors, sometimes 4 pin. Each fan header can be controlled by the bios.
You can read up in your mobo book and might find info here somewhere. or use Google and see what you find.
Or you could buy a fan controller that has sensors you can place anywhere you want and let the controller adjust the speeds.
You'll probably need to redo your fan connectors to the small 3 pin.