Hi @CClark3,
The “Last modified date” is not suitable for this, unfortunately, for the reason you’re describing. It’s not possible to change the behavior of that property or have it exclude certain changes.
If you’re interested in changes to deals, I’d recommend the sales analytics: Create sales reports in the sales analytics suite
(specifically the “Forecasts & Pipeline” section)
These include a “Deal change history” and “Deal push rate” report which might give you out of the box what you’re looking for - or at least close to it.
Best regards!