Think about what you are asking Project to do. You want to manually update a
summary line and have Project "guess" what the Physical Percent (%) Complete
is for the individual task within that summary task. Does this make sense?
Are you sure this is what you really want? Suppose you have 5 tasks under a
summary task. If you could update the summary task to 50% complete, how will
Project know what the percentage complete of each individual task is? You
can't assume they are all 50% complete. So the short answer is you can't
update the summary line because it is designed that way.
HTH
