I'm not sure if it'll help, but you might look at the method I used in my AppWatcher suite, as I faced a similar issue: I didn't want stuff to start happening until after a file had fully copied.
Look at the Wait for install/copy to complete before proceeding group in the AppWatchAdd > App Added macro. Basically, I take two measurements of file size at slightly different times, and only proceed when there's no difference.
-rob.