I don't know which "switch" u think of, however, there's a easy way.
I assume u have a while loop that goes through the recordset and displays every entry like this:
while($row = mysql_fetch_array($result))
{
echo "<option value=\"" . $row["id"] . "\" ";
if($row["id"] == $selectrow)
{
echo " selected=\"selected\"";
}
echo ">";
echo $row["text"];
echo "</option>";
}
So u see, every entry's id is compared to $selectedrow. When u set $selectedrow to the id of some entry, this entry will be selected by default. Actually it's a very simple task, just check every entry and echo the additional html attrib selected="selected" if u wanna select it.
Hope that helps