Smbc,
Not sure if you can point to a custom dictionary.
I know that if I have an abbreviation, someone's name, etc. It will be identified.
If I go into a word document and add those words that are being identified. Then run a grammar/spell check in word, I can add those to the word dictionary. Then next time that you run the vba it should bypass those words.
Fyi, the vba doesn't check words in the sheet background ,nor in a table. I don't recall if it checks multiple pages or only current page.