Hook for when comment added to blog post

Hi,

I’m trying to write a plugin that pops up a message window when a comment is posted to a blog post. At the moment I’m using the action hook

add_action("wp_insert_comment", "function_name");

function function_name(){
    echo "<script>
              mywindow = window.open('http://www.twitter.com', ' ',     'width=300,height=500');
          </script>";
}

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When I post a comment to a blog post I expect the twitter window to pop up but nothing happens. Any help will be appreciated.

Regards,

Anthony