probe-file & file-write-date redundancy?

[Steve Weyer <weyer@apple.com>]

I have an application that is comparing file dates of several hundred files in
each of ~6 directories.  since this is a test that is being performed 
while a user is waiting to check on status of process steps (determining which
files to update or create), I'd like it to be reasonably fast.
currently, to be on the safe side, I usually do:

(defun FILE-WRITE-DATE-OR-NIL (file-string)
  (let ((path (pathname file-string)))
    (and (probe-file path) (file-write-date path))
    ))

however, file-write-date is doing some kind of probe test since if the file
doesn't exist, it generates an error. I was wondering whether there was an
intermediate write-date function in MCL that someone knows of I could call that
would return a NIL instead of generate an error when the file doesn't exist and
thus eliminate the redundant probe-file checking that I'm doing.

thanks

Steve Weyer
Janssen Research Foundation
(609) 730-3056