Good Powerpoint Question

have created a Powerpoint presentation which will run on a kiosk station. I have built 2 presentations, one: the main presentation is formatted in a landscape orientation…the other presentation displays map information which is better suited to aportrait orientation. I have created a interactive button-based navigation system linking the 2 presentations together but the client would prefer a self-running, looping presentation. The question is…does anyone know how to link two shows together that can also run automatically?

One of the constraints, though, is to have a self-running program, with no audience interaction.

Thanks in advance for any input you might have.