DAX flag and dynamic interval measure

Right, you want to exclude enterprises which have an active entry during the period. You can use

VAR CurrentEnterprise = SELECTEDVALUE( 'Table'[Enterprise] )
VAR NumDays = SELECTEDVALUE( 'Num days'[Num days] )
VAR StartDate = TODAY( ) - NumDays
VAR ChosenDates = CALENDAR( StartDate, TODAY( ) )
VAR InactiveEnterprises =
	CALCULATETABLE(
		VALUES( 'Table'[Enterprise] ),
		TREATAS( ChosenDates, 'Table'[Date] ),
		TREATAS( { 0 }, 'Table'[Flag active] )
	)
VAR ActiveEnterprises =
	CALCULATETABLE(
		VALUES( 'Table'[Enterprise] ),
		TREATAS( ChosenDates, 'Table'[Date] ),
		TREATAS( { 1 }, 'Table'[Flag active] )
	)
RETURN
	IF(
		CurrentEnterprise IN
			EXCEPT( InactiveEnterprises, ActiveEnterprises ),
		1
	)