Simple:
make an enum field 'display' wid 'y' and 'n'
in the form give an option field
then in php code
<?php
$connect = mysql_connect($host,$user,$pass);
$db = mysql_select_db($dbname,$connect);
$sql = "SELECT `display` FROM `table` WHERE `user` = '".$some_user_variable."'";
$query = mysql_query($sql,$a);
$fetch = mysql_fetch_rows($query);
if($fetch[0] = 'y')
{ //Code to display username}
else
{//some other code}
?>
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Paagle
TEAM LEADER-Team Xuberance(
http://www.xuberance.com)