If I understand you right, it is not a fix for the custom app you need, rather something quite separate that disables a clock reset. The ability to change the time is built into the operating system so you need either a customised version of Pocket PC (!) or some other agent that blocks the clock reset (or otherwise nullifies it by reverting to the synched time). Whatever program is set running must itself be incapable of disabling by the employees or else must leave some evidence of having been disabled so in principle you can check whether your employees have disabled it. Well, understanding the problem is a start. Modifying Windows is not realistic within a sensible budget or time-frame - something more imaginative is needed. I'd suggest a program that auto-starts, hides itself as much as possible, keeps resetting the clock to the required (synched) time and leaves a carefully hidden trail in the registry that would require your employees to be IT professionals to stand a chance of hiding the fact they've messed with the clock.