Info about menu design

Hi guys,

Trying to create a menu but it doesn't seem to work and would like advice with it. BTW I'm sorry if I'm posting in the wrong section I'm just not sure if it goes in the themes section or anything else. So here it goes.

I'm using the primary_link of drupal to create my menu but I'm using a different image in the background for a nicer feel to the menu.
Here is a little sample of what my menu looks like and how I get to it.

  <tr>
    <td class="mirrortab_first" />
    <td class="mirrortab_active_first" />
      <?php if (isset($primary_links)) { ?><?php print dune_primary_links() ?><?php } ?>
    <td class="mirrortab_last" />
  </tr>

The php Fucntion

function dune_primary_links() {
  $links = menu_primary_links();
  $i = 1;
  if ($links) {
    foreach ($links as $link) {

      if ($i == 1)
        $output .= '<td valign="top" class="mirrortab_active_back">' . $link . '</td>' . '<td class="mirrortab_active_last" />';
      else
        $output .= '<td valign="top" class="mirrortab_back">' . $link . '</td>';

      $i++;
      
    } 
  }
  return $output;

and the result on my Webpage

  <tr>
    <td class="mirrortab_first" />
    <td class="mirrortab_active_first" />
    <td valign="top" class="mirrortab_active_back">
      <a href="/apache2-default/intranet/?q=nouvelles" title="Nouvelles" class="active">Nouvelles</a>
    </td>
    <td class="mirrortab_active_last" />
    <td valign="top" class="mirrortab_back">
      <a href="/apache2-default/intranet/?q=formation" title="Formation">Formation</a>
    </td>
    <td valign="top" class="mirrortab_back">
      <a href="/apache2-default/intranet/?q=repertoire" title="Répertoire téléphonique">Répertoire téléphonique</a>
    </td>
    <td valign="top" class="mirrortab_back">
      <a href="/apache2-default/intranet/?q=contact" title="Contactez-Nous">Contactez-Nous</a>
    </td>
    <td valign="top" class="mirrortab_back">
      <a href="/apache2-default/intranet/" title="A Propos">A Propos</a>
    </td>
    <td class="mirrortab_last" />
  </tr>

As you can see I have to type of menu one on top of the other(mirrortab and the mirrortab_active) The mirrortab_active is the selected menu. But now I have no clue how to make it change when the user is click on the second menu..

Hope you understand my problem.

Cheers