[AUCTeX] how to make compile region to include some command in main document

[waterloo]

for doing with chinese ,  I need \begin{CJK*}{GBK}{kai} 
immediately after \begin{document} and \end{CJK*} immediately before  \end{document} .

but when I use compile region and preview of auctex , it only include preamble before \begin{document} and a lonely \end{document}.

How to make it include \begin{CJK*}{GBK} and \end{CJK*} . 

I use texlive2008 DVD emacs23 auctex11.85 in gentoo .

thanks