Nav menu border & position adjustments?

[o0bergo0ber]

greetings,
our site has the usual fly-out type of navigation menu. colour, position & borders etc are controlled by css.
the question i have is, how can i give the uppermost fly-out nav item a border on the top, without the one's below having a top & bottom border [therefore essentially making 2px between items when there should only be 1px] you know what i mean yeah? obviously i want the bottom item to have a bottom border, not a top [if you follow].
also, is there a way to control position of the 3rd level nav fly-out, without affecting the 2nd level.
is this kinda clear? i can certainly elaborate if need be.
thanks
Jas

[createErrorMsg]

how can i give the uppermost fly-out nav item a border on the top

html:
<ul>
<li class="top_item"><a href="#">Link</a></li>
<li><a href="#">Link</a></li>
<li><a href="#">Link</a></li>
<li><a href="#">Link</a></li>
</ul>

css:
ul li {
border-bottom:1px solid #000;
}
ul li.top_item{
border-top:1px solid #000;
}

cEM