Jose,
Excel does not have a concept of negative time (or date for that matter) and
will produce an error.
VBA can work with negative time though, so may be UDF will work for you.

Depends on your aim.

NickHK

"Jose G. Jasso" <Jose G. wrote in message
...
trying to see if a formula in excel can calculate negative time. Example
after 40 hours would be displayed as negative time.