I'm trying to assist a wheelchair-bound person develop some presentations using a joystick type of device, specifically a Tash 25320 "Mini Joy". It has 4 directional clicks in the usual 4 directions plus a push down that functions like the left click on a mouse. Problem is we are trying to use it to navigate through each "slide" using the directional clickers, if that makes sense, to correspond with the usual back and forth navigation with the arrows on the keyboard. Does anybody have an idea how we can work with PowerPoint to program the joystick to do this?

thanks very much for any and all suggestions.