There is no event you can trap for a change of the Style name applied to some content. Frankly, I can't see why you're changing the Style name of the content you want to have showing in the StyleRef field; surely it would be better to retain that - and the presently-applied Style names for the content - and, if necessary, change the Style formatting and use a different Style (perhaps based on the current one) for whatever else you're presently re-assigning the Style to. I also don't understand what your use of StyleRef fields has to do with Tables of Contents or Indexing.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]