Actually there is a much better way of doing this. By using metis you are using an external service (namely cmd.exe) to perform the action which means not only will many dos boxes show anddisappear on the hosts screen, but it is slow and wastes resources and even lag the room that's being hosted. If you were to run a WCB plugin you could use native Windows API calls to get a list of all files in a particular directory and then search through the list comparing it to a previous list stored. All of this can be done in memory, with no need to save the information to any external file, reducing I/O process and also speeding it all up This could be done on a loop or alternatively be triggered from within room, even using a "elite" group of ip's to limit who can trigger it.
Hopefully you will use the best approach!