Update values which match the same ip php/sql - php

Question

<?
$nick = $_POST['nick'];
$link = $_POST['link'];
$regiment = $_POST['regiment'];
$message = $_POST['message'];
$date = date('Y-m-d H:i:s');
$ip = $_SERVER['REMOTE_ADDR'];
$servername="localhost";
$username="pp";
$conn= mysql_connect($servername,$username, mygas13)or die(mysql_error());
mysql_select_db("pp",$conn);
$ip = mysql_real_escape_string($_SERVER['REMOTE_ADDR']);
$sql = "SELECT TIMEDIFF(NOW(), `LastPost`) AS 'TimeSinceLast'
FROM `userTable`
WHERE `ip` = '{$ip}'
AND `LastPost` > DATE_SUB(NOW(), INTERVAL 1 DAY)";
$result = mysql_query($sql) or die(mysql_error());
if(mysql_num_rows($result) > 0) {
$row = mysql_fetch_assoc($result);
$timeSinceLast = date("G\h i\m s\s", strtotime($row['TimeSinceLast']));
$sql="insert into userTable (nick,link,message,regiment,ip,date,submitted) VALUES ('$nick', '$link', '$message', '$regiment', '$ip', '$date', 'Yes') ";
$result=mysql_query($sql,$conn) or die(mysql_error());
}
else {
$servername="localhost";
$username="pp";
$conn= mysql_connect($servername,$username, mygas13)or die(mysql_error());
mysql_select_db("pp",$conn);
$sql="insert into userTable (nick,link,message,regiment,ip,date,submitted) VALUES ('$nick', '$link', '$message', '$regiment', '$ip', '$date', 'No')";
$result=mysql_query($sql,$conn) or die(mysql_error());
mysql_close($connection);
}
header("Location: thanks.html");
?>
This is my input.php. It submits the data but it also checks if multiple submissions come from one ip in 1day period. What i can't do is to update the value submitted for the rest of his/her submissions with yes. I have tried DUPLICATE KEY UPDATE but it did not work