Customize grammar checker lexicon

For years I've been stumbling over subtleties in the lexicon used by the
grammar checker, now I'm just irritated enough to ask a question about it.
Like any industry, my area of expertise has its own subtle uses of the
language. For example. i regularly use the word "vulnerability" as a noun.
With a conjugation of vulnerabilities as a plural form of that noun. Easy
right? well I am forever having to ignore the grammar checker when it chokes
on this.

so... Is there any method, whether supported or not, to update the
lexicondata file used by the Office products to include my own rules?

I'd appreciate any response available.

Thanks,

Dion