Just to post a bit of a different route...I have almost the same thing, but I check if a file (a blank text file) exists in a certain spot on the network. At one point I used a table to mark that it should be shut down, but then I had problems with corruption and couldn't get the table check working properly...so we came up with this idea. I like it more now because it's not reliant on databases at all, just running a dir to see if a file exists or not. Hope that helps.
Kevin