Sriram --
No, I do not believe this is possible, as it is handled programmatically in
the software. When a task is marked as 100% Complete, the software assumes
that the task finished as it was scheduled. If you need to establish any
other date as the Actual Finish date, I would recommend that you add the
Actual Finish field to the list of Published fields in Microsoft Project,
and then "push" this field onto each user's timesheets by republishing the
assignments, and then ask your people to enter an Actual Finish date instead
of entering 100% in the % Work Complete field. In fact, you should probably
make the setting of an Actual Finish date part of your company's methodology
for tracking progress and require everyone to use it. Hope this helps.