To see that this would be of any use I'll try to describe what I need it for.
I use a program called "Remote Camera Control" to have a Sony DSLR A700 transfer pictures directly to the harddisk. I even could take pictures from the PC with this tool, but this is not used. I wire up the DSLR and take shots within my studio. So the idea is, that I can view them fullscreen on my monitor (which makes a superb replacement for the DSLR monitor). The pictures a written to a folder I can select.
Basically my idea would be that I start XnView in this folder and start a Quick Diashow (with the "pause" key) it stops at the last picture. When a new picture arrives, XnView continues with that picture. Is that possible ? At the moment I can't change to that new picture even if I hit "PageDown". If that would work a generator of "PageDown" events would to the trick

The Sony tool offers an option to open the pictures in something called "Sony Lightbox". I searched the registry and found a way to open XnView instead. But it seems XnView doesn't like to be started from "remote camera control" because it crashes as soon as the browser opens. I therefor guess that it is not started with the filename as parameter, in which case it should work. Adopting that interface would be the coolest thing to have, but I'm aware that this is almost impossible to adopt without knowing the "protocol" of it.
So, changing to the last picture in a folder (or a new arriving) would be great.