New tab for login page only!

I want to add a new tab to the Drupal login tabs...

I somewhat found that the following will add a tab to all tabs...

function phptemplate_menu_local_tasks() {
if ($primary = menu_primary_local_tasks()) {
    $output .= "<ul class=\"tabs primary\">\n". $primary ."<li><a href=\"#myNewTab\">Ny New Tab</a></li></ul>\n";
}
return $output;
}

But I only want to add a new tab when the user acces the Login page (the Log in, Request new password, Register - tabs)
How can you add a tab to this only, and how can you control what will be displayed when accessing this tab? Could you
somehow say that a certain block should be displayed when accessing my own tab.

Hope someone can help me!