Discrete WIP Job - Completion date

Hi

The discrete WIP Job, completion date is getting defaulted from the scheduled ship date of the sales order when the wip job is created through AutoCreate Final Assembly Orders.

However if the scheduled ship date of the line says 24-JUN-2014 23:59:00, and the WIP job also completes at the same time i.e. WIP job completion date = 24-JUN-2014 23:59:00, its not practical to expect it to be shipped as soon as its completed.

I want the WIP job completion date to be lets say 6 hours or a day before the scheduled ship date of the sales order line.

Is this possible?