I produce slides which are used by a number of people when delivering
training courses.  The trainers all use a slightly different combination, or
order of slides.  

I would rather not keep separate presentations for each trainer especially
as it could mean updating the same slide a number of times (in each
presentation).

What I wonder therefore is whether there is a way of having a 'resevoir' of
slides (or master copy of slides) from which I select certain ones to create
individual presentations.  Ideally I would want to update the master copy and
know that wherever that slide is included in a presentation the corresponding
copy is also updated.

Thanks