what is the name of the mouse wheel in the input

im trying to add a zooming ability in my game. dos anyone know what the mouse wheel is called in the input thing. btw i mean the scroll wheel not the button in the wheel

I want to add that too! But I have no mouse to do it on! LOL, anyways this post might help sum: http://answers.unity3d.com/questions/13115/mouse-wheel-zoom

i dont have answer but i cant scrol out when im editing i cant move please help me