Hi there @dmbantu !
Interesting use case!
The “Hide program stage” program rule will not hide data already entered, but it will prevent the users from adding more events in that stage. Is it an option to make a program rule that will have a “Hide program stage” action that hides program stage A, when the conditions for Locking program stage A is met?
This will prevent the user from adding more events to the stage that is “Hidden” but other stages can be added normally.
“Hide program stage” might not be the best name for this program rule action, it could perhaps be named “Hide the option of adding more events in program stage” (but that is a long name 
)
P.S. You could make a separate condidition for Hiding (the option of adding events in) program stage B separately, if you want to “lock” program stage B based on a separate condition.
Markus