since this is a build-in function from sc2 i wouldn't do this that way.
i guess you want to increase the effect of zooming with the mousewheel.
as far as i know you are able to set the standard gameplay camera. if you change the max height, zooming might adjust to the new value.(cannot say for sure).
if this doesnt work add a dialog with slider and trigger on that. but be warned, at a certain distance sound effects disappear.