Doesnt have to be a batch file, just a simple vb program... I dont really know much about these boxes, so I dont know the file locations or what the keyfile should even look like, lol I would have made it if I did...
A simple VB program, you run it manually or it runs every half an hour, ftp to the box, look in the common directories for the right file, when it finds it, either by the location of the file or by the file contents you should know the type of box and the type e.g TW??? I dont know if this is true as I said I dont know much about the boxes, I only know programming so finding simple solutions is what I normally do.
Anyway so you have the file, you check it on the net at a top secret hidden location against a template keyfile or just the keys themselves, the just ftp the file back to the box, the whole process should take 2 seconds to update then you just reboot the box...
I dont know much about the language the boxes are programmed in but couldnt the box itself have an update option like this that connects to the net and updates its keys?