怎樣可在Microsoft Word 內將語言互轉？

What you want to do is translation. MS Word is not a translation programme. Buy one on use the free internet translation web.
http://babelfish.altavista.com/
http://www.freetranslation.com/
繁轉簡 or 簡轉繁 is not translation as their source code is the same. Just a different layout only.