Adding to the bbcode list

Hi

I want to let users put

[url]http://www.raincheck.co.nz[/url] into their bbcode.

$this->add_tag(array('Name'=>'link','HasParam'=>true,'HtmlBegin'=>'<a href="%%P%%">','HtmlEnd'=>'</a>'));

This is the code for a link. I'm not sure how to update it to allow for
[link][/link]
and
[link=][/link]

any ideas?

thanks

Sarah