LED turn on in a certain range

I am working on a project where I use a magnetometer To pick up on large metal mass and I want to switch on one LED if It picks up a metal mass (magnetic north changes) and another if there is no metal mass?? So it must detect where magnetic north is and than set on that heading and an LED must be on and as a metal mass is placed infront of the sensor its heading will change by 10 degrees or so, and the other LED must be turned on. So i need a range for the LED to turn on and off.can someone help?

Do you have a magnetometer? Do you know how to use it? What programming and hardware experience do you have? Have you done any research?