Displaying rolled up duration for external tasks

[David L. Goad]

Folks,

I have a summary project plan which is mostly a collection of
tasks/milestones which have no duration per se, but have as
predecessors several external tasks.

I can nicely show those external tasks and their durations, but the
durations are not represented in the tasks which have them as
predecessors. As an example, I can have a milestone with nothing but
6 external predecessors with durations of anywhere from several days
to several months. However, the rollup task indicates only 1 day of
duration. Is there any way to include the duration of external tasks
in the rollup task for tasks with external task predecessors?

Thanks,

-dave