This should do the work. You don't need extra steps. Now just make sure you restart the context and make a test. jforum's bbcode processor will try to match your regex aginst the text.
Rafael [originally posted on jforum.net by Rafael Steil]
It worked for me. However, I didn't used the <td> tag, as it will break the layout. I suggest you to do the same (eg, just put the <embed> tag there, "alone").
To add the tag to the new post / reply form, edit the file templates/default/post_form.htm
Rafael [originally posted on jforum.net by Rafael Steil]