Reliably confirming a successful file save in Windows

[Stephen King]

Hi

Is there any way of reliably confirming if a file (in this case a substack)
has been successfully saved or not? The docs state that if the result is
empty then the save has been successful, but I am finding that this is not
reliable.
I am working on a network so saving can sometimes be delayed. Checking the
result straight after the save yields empty anyway. Even waiting a few
seconds still gives empty when trying to write to a read only file. Waiting
long enough (does ultimately give the "Can't open.." result but this is a
variable.

The problem seems to be Rev continues the script without waiting for the
result. Is it possible to halt the handler until the result becomes valid?

By the way, this is on windows XP. I am using 2.5.1 at present as my project
is in this version. I have upgraded to 2.8.1 but would prefer not to mix on
this project as it is near completion.

Cheers
Steve