Updating Multiply Fields In List Page

i refer to that very nice and interesting topic
http://www.asprunner.com/forums/topic/14188-updating-multiple-selected-records-based-on-a-combobox-value-on-list-page/
i tryied but is not working i use phprunner 6.2
can you help ?
what i have done so far is

to add following dropdown combo box in list page
// dropdown to select category to update requested items
global $conn;

$str = "";

$str.= "<select name=\"JobDropDown\" id=\"JobDropDown\"><option value=\"\">Select Category :</option>";
//select values from database

$strSQL = "select categories from categories";

$rs = db_query($strSQL,$conn);

while ($data = db_fetch_array($rs))

$str.="<option value=\"".$data["categories"]."\">".$data["categories"]."</option>";

$str.="</select>";

echo $str;
which is working and i can see the field names
i add a custom button next to combo box above which i need user to press and update the selected records with the value of the combo box
// on before client button event
var value = document.getElementById('JobDropDown').value;

alert (value);
//on server tab
global $dal;
for ($i=0; $i<count($keys); $i++)
{
// set ReportsTo field to 'Bob Smith'
$sql = "Update requsitions set category='Bob Smith' where ID="
. $keys[$i]["ID"];
CustomQuery($sql);
}
$result["txt"] = "Records were updated.";
// on client after
var message = result["txt"];
ctrl.setMessage(message);
i need help to change 'Bob Smith' with the value of the dropdown combo box
pls help