Right Click Zoom

I am currently makeing a game. :smiley:

I have alot of confusion on how to make a zoom when you press right click.

What i plan to do is be able to press right click and that will activate the zoom
(what would be best is once i am zoomed in to be able to control the amount of zoom with the up and down arrows, but thats after i get the zoom to work)

How do i make a zoom?