How do I Make a Scrolling in and out mechanic?

I am making a game and I wanted the ability to scroll to zoom in, and scroll to zoom out, and I can't seem to figure it out.

On mousewheel up

--- Set LayoutScale to LayoutScale + 0.5

On mousewheel down

--- Set LayoutScale to LayoutScale - 0.5

Replace 0.5 with the amount you'd like it to resize by.

~Sol

Zoom & pan example:

https://drive.google.com/file/d/0B-xiqK ... sp=sharing