Promise Date, Request Date, Schedule ship date to be independent to each other

our business scenario is such that sales user when creating & booking the sales order , he can enter the Promise date, Request date , Schedule Ship date to be independent to each other, sales user can add any date in Request Date, Promise date & by overiding  ATP he changes the schedule ship date

as on date request date is sys date when order is created  & in some order i can change the promise darte & in some order it  is not  allowed to change it is taking the date as Request Date

please advise