Multiple options in custom bbcode

[Aurons Ghost]

I have a story archive associated with my site and I am trying to set up some bbcode that can easily link to those stories and to chapters within those stories.

story urls are http://stories.mysite.net/viewstory.php?sid=Story ID
and chapter urls are http://stories.mysite.net/viewstory.php?sid=Story ID&chapter=Chapter number

I know I can get the first to work simply with:

[story={option}]{param}[/story]
<a href="http://stories.mysite.net/viewstory.php?sid={option}">{param}</a>

but I don't know how to do the second, or even if it's possible. I think it should be like this:

[chapter={option1},{option2}]{param}[/chapter]
<a href="http://stories.mysite.net/viewstory.php?sid={option1}&chapter={option2}">{param}</a>

I would guess I need to make a plugin for this to work, how would I go about doing this, if it's possible at all?

(I'm on 3.5.4 if that's any help)