Adding code to a document, whether via a class module or something else, is unlikely to prevent bookmark deletion. Yes, bookmarks are fragile, being easily deleted and/or having content either included or excluded unintentionally but they're not the only 'containers' you can use in Word, plenty of which are more robust than bookmarks. Depending on what you're trying to do, you could use a table, Style, Section, content control or field, for example, to hold the same content. And, as already discussed, there's document properties and variables.

As for 'private' solutions, MS doesn't engage in those, so contacting MS for one won't get you very far. Often, too, you'll find users with a better knowledge of how to do some things than the MS technical experts.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]