PopUp Vindue i Form?

Jeg har en form, som man udfylder som kontakt, og jeg vil gerne at den besked der kommer frem IKKE kommer i samme vindue, men enten i en popup box eller i et nyt vindue....

Hvordan klarer jeg lige den??

Her er min kontakt.html:
<form name="myform" method="post" action="formmail.php" target="_blank">
   
    <table width="100%">
    <tr>
        <td>Navn:</td>
        <td><input type="text" name="name"></td>
    </tr>
    <tr>
        <td>Email:</td>
        <td><input type="text" name="email"></td>
    </tr>
    <tr>
        <td valign="top">Besked:</td>
        <td><textarea name="comments" cols=35 rows=5></textarea></td>
    </tr>
    </table>
<input type="submit" name="Submit" value="Send">
<input type="reset" name="Reset" value="Slet">
</form>

Og her er min Formmail:
<?php
  $name=addslashes($_POST['name']);
  $email=addslashes($_POST['email']);
  $comments=addslashes($_POST['comments']);

// you can specify which email you want your contact form to be emailed to here

  $toemail = "myemail@mydomain.com";
  $subject = "My contact form submission";

  $headers = "MIME-Version: 1.0\n"
            ."From: \"".$name."\" <".$email.">\n"
            ."Content-type: text/html; charset=iso-8859-1\n";

  $body = "Name: ".$name."<br>\n"
            ."Email: ".$email."<br>\n"
            ."Comments:<br>\n"
            .$comments;

  if (!ereg("^[a-zA-Z0-9_]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$", $email))
  {
    echo "That is not a valid email address.  Please return to the"
          ." previous page and try again.";
    exit;
  }

    mail($toemail, $subject, $body, $headers);
    echo "Thanks for submitting your comments";
?>