Border on hover?

Hi again,
I'm having difficulty figuring out how to create a top-border on my main menu sub-category, on hover.

Here's what I'm trying to accomplish:

Parent item (no border)
Sub-category (top solid border)
Sub-sub-category (right solid border - while keeping the border on the previous category too)

Is this possible? I'm sure it is. I just don't know where to change it.

Development site (http://dev.yourbusybee.com/ice/)

Thanks in advance.

~Laura

#parent { }
#parent .sub { }
#parent .sub:hover { border-top: 1px solid blue; }
#parent .sub .sub { border-right: 1px solid red; }

Like thatt?

Conceptually, yes. But I'm not having much luck figuring out how to do that with the specific css I've got to work with (I'm using a template and have made significant modifications to it).

Then it would depend on the code you're working around. Perhaps you should post that part, or just point out which thing it is on your page you linked.