You could switch to 1904 date system, ToolsCalculate1904 date system

--
HTH

Bob Phillips

(replace somewhere in email address with gmail if mailing direct)

"Huong Son" <Huong wrote in message
...
I have a calculation like this (7/6/2006 6:10 AM) - (7/6/2006 6:20 AM) =
#######
How can i sole this problem