open different pages on doing login

i have four pages that would be displayed on when user gets login otherwise a popup is displayed please login and login page gets open. when user writes username and password the only 1st page every time gets open. i want to open 3rd page but every time page 1 gets open... please tell me a way to open every separate page when user logs in... like

<?php
$con = mysql_connect("localhost","root","");
$db = mysql_select_db('fyp',$con);

if(isset($_POST['login']))
{
$user_name = $_SESSION['user_name'] = $_POST['user_name'];
$user_pass = $_POST['user_pass'];


$query = "select * from user_login where user_name='".$user_name."' AND user_pass='".$user_pass."'";
$run = mysql_query($query);
if(mysql_num_rows($run)>0){

echo "<script>window.open('register_event.php?logged=logged in Successfully..!!!','_self')</script>";   // it is the page 1
echo "<script>window.open('register_executive.php?logged=logged in Successfully..!!!','_self')</script>"; // it is page 2
}
else{
    echo "<script>alert('password or user name is incorrect!')</script>";
}
}

?>