I do the exact same thing as Wayne except check for a bit in an SQL table. Additionally, I utilize a startup program. I basically have 3 executables. The first executable is a startup program. It checks the bit to make sure it is ok to log in. If it is, it checks the dates and times on the files for the other two executables and runs the latest version. When I compile a new executable with changes I save it over the older executable version. Next time someone starts the application the start .exe will use this one instead. This way I don't have to boot anyone from the system, unless it is a real important change. If you do something similar, pass a parameter from the first .exe to the second so the user can only start the application using the first .exe. Provide them with an error message if they attempt to run the other. Once set up this is very easy to maintain.