Levels pallet mac/pc

ok, in the levels pallet on the mac you can hold down the option key while draging the sliders and have photoshop take your entire screen and fill it with black or white depending on what slider you are dragging (highlight or shadow)

now with this you can find the exact area in a photo that is either the darkest or the lightest (try it)

-I know there are other ways but I use this every day on the macs at work-

now what I want to know...is what is the keystroke to do that on the PC?
Its not "alt" like you would think it would be.
Did Adobe leave it out of the PC versions of PS?

I think its safe to say....nobody knows :(

I'll ask adobe!