Events and Plotting

I need to interrupt Acad's plotting/publishing of multiple layouts to insert
an object in PS prior to plotting.

My code, Using Events, ie. beginPlot and/or LayoutSwitched, all works well
on single layout instances or when the user selects the layout manually,
plotting one layout at a time.. If multiple layouts are selected, the code
is ignored.

This idea also needs to be applied to plotting/publishing with the sheet set
manager. I can't find a way to "catch" the autocad plot/publish process as
each draswing or layout is being accessed.

The code must be transparent to the user, hence the events approach.

Any ideas where to go to find a direction?

Thanks ahead of time.
Jim