Is there a conditional I can use in postbit for the forumid?

[coolegg]

I want to modify my postbit so that the first post of every thread in my Articles forum has a different look, because I want to give my Articles a more professional look that stands out over that of the comments/replies that will follow and other posts on the site.

I have half the conditional...
$post[postcount]==1
...to identify it as the first post of the thread

But how would I test if the post is in the forum with id number 3 (my particular Articles forum id)?
By trial and error I have tried...
$post[forum]==3
$post[forumid]==3
$post[forum_id]==3
... so far, with no luck.

And as an aside... is there a list of the vB variables and what they mean? ie
$post[post] means ....
$post[usertitle] means ...
$post[rank] means .... and so on.

Edit: I perhaps should have said... I am using vB3

Edit again: I'll answer my own question since I stumbled across the answer by good ole trial and error. The complete conditional is:

<if condition="($forum[forumid]==3)&&($post[postcount]==1)">

Is there a legend/list of these variables and what they mean? $forum[X], $post[X] and so on? trial and error is fun but time-intensive. :ermm: