How do add new proofing languages to Microsoft Office 2011 for Mac? How is possible to add new spellchecking languages to Office 2011 for Mac?

I am referring to languages that are not listed in the relatively small (~20) default list of languages.
It is impossible, but a good place to ask might be the forums run by MS for its products:

http://answers.microsoft.com/en-us/mac/forum/macword