Backend Event Question

[Hoagie]

Hello all.

I am currently working on a multi window (JDesktopPane)
application. The low level data structure is a "Project" containing
several "Scripts."
Since I have multiple windows which are interested in the
current state of other windows (e.g., one window shows all the events
in a script, while another shows the currently selected event), I am
wondering what is the considered the proper way to notify these
windows of changes within the Project class?
Is it "more proper" to use Observer/Observable when watching
data structure classes for changes, or should I set an custom
Event/Listener relationship between the data structure and the items
interested.
Just looking to "do it right the first time." Thanks for
any pointers!