change schedule finish date work order mannually

Hi Experts,

In our company there are rules delivery date on Purchase Request (PR) at least 7 days from the PR release date (PR created).

For PR service that generated from Work Order, delivery date = shced finish date (default in system is scheduled finish dates

depends on total work hours in tasklist and scheduling type),but i want to change manually "sched finish date", how to do that?

Please any help would be very appreciated.