First person camera restriction.

Well, this is kinda hard to explain but I will try my best. I want the first person camera to have restriced movement, by which I mean the camera can only look 90 degrees left and right and 90 up and down. The camera is static so it can't "walk". An example of what I'm on about, could be like call of duty when your in a veichle, you can only look in a certain area. I've looked at the code of the default script and changed a few values but can't seem to do anything.

Any help at all would be awesome

Take a look at the script MouseOrbit.js in the "Standard Assets/Scripts/Camera Scripts" folder. There is an advanced example for clamping camera pitch (which you can use as a starting point).