Hi Heli,
The core spellers aren't accessible for changes although you can add custom dictionary (word) and exclusion lists. You may want to
use the link below to also post in the MS Word Spelling & Grammar discussion group with some examples. Some of the MS folks who
create those tools are there from time to time.
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Using the Proofing Tools, I have found an unacceptably high frequency of
mistakes in the Finnish Dictionary. How can I make changes in the dictionary?>>
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Please let us know if this has helped,
Bob Buckland ?

MS Office System Products MVP
LINKS
A. Specific newsgroup/discussion group mentioned in this message:
news://msnews.microsoft.com/microsoft.public.word.spelling.grammar
or via browser:
http://microsoft.com/communities/newsgroups/en-us/?dg=microsoft.public.word.spelling.grammar
B. MS Office Community discussion/newsgroups via Web Browser
http://microsoft.com/office/community/en-us/default.mspx
or
Microsoft hosted newsgroups via Outlook Express/newsreader
news://msnews.microsoft.com