Full width absolute pos div inside td

Trying to keep an absolutly positioned, 100% width div inside it's containing TD.

HTML

<table id="OuterTable" border="1">
    <tr>
        <td id="TableCell">
            <table id="InnerTable" border="1">
                <tr>
                    <td>Dummy text of varying length</td>
                    <td>Dummy</td>
                </tr>
            </table>
            <div id="AbsoluteDiv">
                <div id="InnerDivLeft">Left Div</div>
                <div id="InnerDivRight">Right Div</div>
            </div>
        </td>
        <td>
            <select multiple="multiple" size="10">
                <option>Varying length options</option>
            </select>
        </td>
    </tr>
</table>

CSS

#OuterTable {
    position:relative;
}
#TableCell {
    vertical-align:top;
    position:relative;
}
#AbsoluteDiv {
    background-color:red;
    position:absolute;
    width:100%;
    bottom:30px;
}
#InnerDivLeft {
    float:left;
}
#InnerDivRight {
    float:right;
}