Best way to update an open PowerPoint presentation

In our lunchroom we have a pc that displays an endless PowerPoint presentation, so the file is always open. The pc does NOT have a keyboard or mouse, so tampering is a little more difficult. Also the pc is running PowerPoint 03 Viewer.
What is the best way to make updates to the PPT/PPS? Script? Macro? Keep in mind that viewer can not call imbedded objects.

I am currently running a script in the startup and rebooting the pc to get the slideshow updated.

Thanks for any help!