How to detect when a project file is closes, or opens?

Hi There,

Is there an event that AE broadcasts that allows a callback to be executed when a user closes or opens a project file from the main File menu. There are some variables in my script that I need to re-initialize when this occurs, but am unsure how can do this.  I've taken a look at the app and project objects in the documentation, but did not find anything that pertains to this.  Are there any techniques out there for initializing variables when a project file closes or opens?

Thanks,

Arie