BOOL LockFile ( HANDLE hFile, DWORD dwFileOffsetLow, DWORD dwFileOffsetHigh, DWORD nNumberOfBytesToLockLow, DWORD nNumberOfBytesToLockHigh); BOOL UnlockFile ( HANDLE hFile, DWORD dwFileOffsetLow, DWORD dwFileOffsetHigh, DWORD nNumberOfBytesToUnlockLow, DWORD nNumberOfBytesToUnlockHigh);