Impress slide show keyboard shortcuts/functions customization

How do I change the keyboard shortcut/function mapping for the slide show mode of Impress?
More specifically, I’m trying to reverse the current functions for Page Up and Page Down (Play next/previous effect) in slide show mode.

I tried making the change through the menu item and it worked while in the editing mode, but not while in the slide show mode. If the change cannot be done from the program’s menus, I would be glad to go about it a different way, such as changing a .ini file.

Thank you!