Writing to unique filenames

Hi,

I'm looking for a method that will write the message to filenames
(numbers, to be precise) in ascending order (1, 2, 3) and won't overwrite
currently-existing files.

I remember a method being discussed of a reply-system (for support) being
created that generated ticket numbers. Can't find the discussion, but I
would imagine this is roughly the same recipe.

Thanks!

-- 
Brock Rozen                                              
brozen(_at_)torah(_dot_)org