Bob - here are the results I get where #### is a negative value.

A B C
10/02/2006 02:12 13/02/2006 06:33 14:33
09/02/2006 08:00 09/02/2006 08:33 0:32
11/02/2006 02:12 13/02/2006 06:33 ####
12/02/2006 02:12 13/02/2006 07:00 ####