I'm thinking this would take an edit to the word VBA code that would extract the zotero id from each reference and then send that list to zotero or directly invoke the zotero export dialog with that list.

There are two different things here: extracting citation data from Word documents, and having some way for Zotero to know (and indicate) which items have been cited in which documents.

Seems to me the second one would be much easier to realise than the first. Through the interaction with the Word plugin Zotero already 'knows' what items are being cited. I'm sure many users would love to have a pseudo-collection 'Cited', with subcollections for document names. Zotero would add and remove items from these subcollections concurrently with interacting with the Word plugin. This would make it easy to export the collection elsewhere, or to put it in a public group. Right now it is surprisingly difficult to replicate a bibliography of sources cited someplace else; that should be one of the easiest things to do.

I've been needing a feature like this for a long time. This time I was asked to send someone PDFs of all the articles I cited in a paper. Right now this means manually going through my library of thousands of articles to find dozens and dozens of articles.

The Zotero 3.0 beta doesn't yet import references from a document, but it is capable of formatting a document with references in it that aren't in your Zotero library. However, we have plans to import references before 3.0 final.

Which feature?
Zotero can store references in a document "it allows other users to work with your Zotero citations and bibliographies without using a Zotero group"): http://www.zotero.org/support/word_processor_plugin_usage#document_preferences
but can't import references from a document as far as I know.

I was thinking about the second part. Thank you anyway