<table onmouseover="SelectCell()">
<tr><td>11</td><td>12</td><td>13</td></tr>
<tr><td>21</td><td>22</td><td>23</td></tr>
<tr><td>31</td><td>32</td><td>33</td></tr>
</table>
<script language="javascript">
function SelectCell()
{
var e = event.srcElement;
if (e.tagName == "TD")
{
var r = document.body.createTextRange();
r.moveToElementText(e);
r.select();
}
}
</script>