DropDown to DropUp

Hi guys

I have the following CSS code:

#ddm {
    list-style: none;
    margin: 0;
    padding: 0;
}
#ddm li {
    float: left;
    width: 75px;
    margin: 0 1px;
    background: #900;
    text-align: center;
    border: 1px solid #009;
}
#ddm a {
    color: #fff;
    display: block;
    text-decoration: none;
    padding: 2px 0 3px;
    width: 75px;
}
#ddm a:hover {
    background: #000;
}  

#ddm li ul {
    position: absolute;
    width: 75px;
    left: -5000px;
}

#menu li ul {
    position: absolute;
    width: 75px;
    left: -5000px;
}

and the following code in my footer:

<ul id="ddm">
    <li><a href="#">Latest Posts</a>
        <ul>
            <li><a href="#">Post One</a></li>
            <li><a href="#">Post Two</a></li>
            <li><a href="#">Post Three</a></li>
        </ul>
    </li>
</ul>

How can I get the menu to ‘drop up’ rather than ‘drop down’ when one hovers over it?

Many thanks

Kenneth Watt