order by column that is result of sum()

I have a query which joins results from two tables one regarding members informaiton and another with monetary values attributed to them.

One of the columns uses a result from sum(), summing a dollar amount. I want to order the results of the query by that particular column DESC so that the larger summed amount is at the top of the list.

Here is my current query:

$selrecord_yma = "2010";
if (isset($_POST['selrecord'])) {
  $selrecord_yma = (get_magic_quotes_gpc()) ? $_POST['selrecord'] : addslashes($_POST['selrecord']);
}
mysql_select_db($database_bninsteins_mysql, $bninsteins_mysql);
$query_yma = sprintf("SELECT s.member_id, s.year, SUM(s.amount) AS 'memberTotal', b.status, b.first_name, b.last_name FROM SMTM AS s JOIN members AS b ON s.member_id = b.member_id WHERE s.year = %s GROUP BY b.status, b.last_name, b.first_name ORDER BY 'memberTotal' DESC", GetSQLValueString($selrecord_yma, "int"));
$yma = mysql_query($query_yma, $bninsteins_mysql) or die(mysql_error());
$row_yma = mysql_fetch_assoc($yma);
$totalRows_yma = mysql_num_rows($yma);


I have also tried ordering by s.amount with no success. It comes up with and order, but not numerical.

The sum() works properly, but the order by doesn't result in a greater to lesser amounts list of rows.

Thanks for your patience as I am not sure I am even asking this question correctly. I appreaciate your help.