I have a requirement to allow users in a specific profile rights to change a few fields and no rights to edit ANY of the other fields for a closed opportunity.  A validation rule would probably be problematic without a way to ensure hundreds of other fields were not changed. 
i.e. page layout has 10 fields, when open the user can edit all 10.  Once closed the user can only edit 2 of those.  With 10 fields I expect something like: 

NOT(
	AND(
		IsClosed, 
		OR(
			ISCHANGED(field a),
			ISCHANGED(field b)
		), 
		NOT(
			OR(
				ISCHANGED(field c), 
				ISCHANGED(field d), 
				...
				ISCHANGED(field j)
			)
		)
	)
)

It would be for too long of a formula to do this with 100 fields where only 2 or 3 can be edtied. 
Do I need to resort to apex?