Sublime Text 2 - writing a script to process multimarkdown

There is an excellent package to preview markdown written using sublime text. I wanted to know how I might modify it, or perhaps use it as the basis for writing one that could process multi-markdown.

I'm using Linux (Ubuntu) and I'm currently calling multimarkdown in the terminal on each file.

One of the issues I think I might face is that multimarkdown refuses to parse an open file for some reason.

Any thoughts on how I might begin this or if an alternative solution exists would be very gratefully received.

There is a MultiMarkdown option in the syntax list - View > Syntax > Markdown > MultiMarkdown. Isn't that working? By the way the syntax (and almost any other) files are in packages folder of Sublime Text 2. This is the syntax file:

/Users/[username]/Library/Application Support/Sublime Text 2/Packages/Markdown/Markdown.tmLanguage

And MultiMarkdown file is in the same directory.