Disable clock edit on windows 6.5

Question

i want to disable edit in clock at windows 6.5 .. i have many people in our company edit date and time to abuse ..

so i want to close this case by disable any edit in date&time .. ..and i searched many times and i didn't find any code

i find this code ..

System.Byte[] offValue = new byte[1];
        offValue [0] = 0x30;
        OpenNETCF.Win32.RegistryKey registryKey = 
        OpenNETCF.Win32.Registry.LocalMachine.OpenSubKey(@"\Software\Microsoft\Clock\", true);
        registryKey.SetValue("AppState", offValue);
        registryKey.Close();

but didn't have OpenNETCF dll or reference to run this code