[Cryo]

You could use a PHP script in your forum home directory like this...

PHP Code:

<?

include("./global.php");

$get_SQL = "SELECT 
                a.userid,
                a.username,
                a.homepage
            FROM 
                ". TABLE_PREFIX ."user a, 
                ". TABLE_PREFIX ".usertextfield b
            WHERE
                a.userid = b.userid
                AND b.signature = \"\"
            ORDER BY
                a.userid ASC";

$get = mysql_query($get_SQL) or die(mysql_error());

while ($g = mysql_fetch_array($get)) { 

    $update_SQL = "UPDATE 
                        ". TABLE_PREFIX ."usertextfield 
                    SET 
                        signature = \"". mysql_real_escape_string($g["homepage"]) ."\" 
                    WHERE 
                        userid = \"". $g["userid"] ."\"";
                        
    $update = mysql_query($update_SQL) or die(mysql_error());
                        
    echo "". $g["username"] ."'s signature has been updated.<br />";
    
    }
    
echo "All done!";

?>

It will run an update that will make all signatures the user's homepage.