ASP includes files in Japanese?

I'm building a Japanese site where the pages are of Charset: charset=Shift_JIS in classic ASP. The text on all the  pages that have the Charset set to Shift_JIS appear fine. However any "include" file which has Japanese characters does not correctly display the Japanese characters within Parent file. The includes files do not have any "Charset" set as they do not have a "head" area.

I can take any given Japanese include file and "Modify> Page Properties...Title/Encoding" and set to the Encoding to "Japanese Shift JIS". This chnages the underlying Encoding to Shift_JIS. However closing dreamweaver and revisiting the same pages I need to start all over again as the underlying Encoding for the includes file is lost (and reverts back to Western ISO Latin1).

This situation is made far worse as, on going back to the includes files, changing their encoding through "Modify> Page Properties...Title/Encoding" the Japanese text is no loger visible-just a series of odd characters. I then need to go to a temporary file that I keep with the Encofding set in the head area, copy the Japanese text from there past it into the includes file and save. I have to do this EVER TIME I edit a file.

I would have expected the includes files to at least encode to that of the Parent file so that I could make sense of the parent file in dremweaver.

Is there a workaround to this apart from not using includes files?

Thanks

DW CS4

MAC 10.6.8