Hi Pamela,
I don't know of a way using a Project Status value (e.g. making it On Hold would also "freeze" the project), but instead, suggest you create a Billing Record (e.g. "*** DO NOT DELETE ***") and mark it as Billed, which has the longstanding pleasant side effect of thereby preventing the project from being accidentally deleted. In fact, this (automating such do-not-delete billing records) is one of the uses of our Auto Bill solution.
Regards,
Doug
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