Cascading / Depending menus left to right

Hi everyone, first question as a paying user (woo hoo)

I've reviewed several tutorials about creating droplist style menus. All good there - but has anyone pulled off one that works left to right and stacks up menus, rather than top to bottom?

 What I have in mind is:

Far left of screen is a circle. Hover on it to open up a list layer to its right, three circles A, B and C. Hovering over circle A opens up a second list with three more circles 1,2 and 3 which will jump to slides when clicked. There is a little bit of space between lists as you go left to right.

Logically, this is a dependency sort of situation, and would be very similar to a website shopping menu, where you pick a category, then a sub category extends off it, and you choose again. If you move your pointer outside of the menus, they disappear.

I've gotten the cascading part down moving to the right, but making the current menu disappear when you move back to the left is escaping me. The invisible border box/hover shortcut doesn't seem to be working. Has anyone given this a shot, or know of a post?

 

Thanks,

Blair