Restrict desktop access while factory ap

We have a factory app that runs on dedicated NT 4.0 computers. Is there a
utility or software (API call) that we can implement to prevent users from accessing the desktop via “CTRL-ESC” key sequence while our app is running? Ideally, we would then like to re-enable it, if a supervisor enters a password from our system to close our app. There is no mouse attached to these systems. We can “kill” the “start-button” via the API call of CloseWindow() to the start-button window. However, we cannot utilize the start menu once we exit our app for admin/maintenence purposes.