D2,

   Is the file being copied part of a controlled environment?  In other
words, is the file being copied as the result of an operation from a client
which you have control over, or is it meant as a general file monitoring
system?

   There was a system where I needed to process files once they were
dropped in a directory.  I wanted to use the file system watcher, but I
couldn't know for sure when the writing of the file was complete.  Because
we were in control of the client, we made it so that the client wrote a zero
byte marker file which would tell the FileSystemWatcher when to process the
original file.  Since the marker file was zero bytes, one could reasonably
assume that the marker file and original file were both closed by the end of
processing.

   Perhaps you could do something similar?