Michel,
I recently incorporated a spell-check method using Office Automation. I take the memo that the user enters, and create a word document and insert the text as a document. Word has a collection called Word.ProofReadingErrors that you can use to identify spelling errors.
I can post the code, if you're interested. (No secret to it, if you get on MSDN and do a search on automated spell checking, you can find similar code examples). I think over on the Foxforum, different people have posted code over the years on implementing spell checking.
Kevin