Your post is unclear.

First you say you want to "auto-fill all check box form field bookmarks (in field settings) in a document", but checkboxes only have true/false states.

Then you say you want to "write a macro in Excel to auto populate an Excel sheet based off of which check boxes are marked".

What are you trying to populate? Word or Excel?

As for "I'd like to use numbers 1 - 3,500 but I don't think that's possible", why does it matter whether they're bookmarked?

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]