I don't really follow what it is you are after but I would suggest using two
columns, one for extra time and one for time off.

I assume from the 7.5 hours day you are entering the hours worked as numbers
not XL times so

Time taken off would be:
=IF(E3=7.5,"",7.5-E3)
and extra hours worked would be:
=IF(E3<=7.5,"",E3-7.5)

If you want to record them both in the same column with time taken off shown
as negatives then simply:

=E3-7.5

will do both.

If you want something different then post back


--
HTH

Sandy
In Perth, the ancient capital of Scotland
and the crowning place of kings


with @tiscali.co.uk


"JDB" wrote in message
...
Hi,

I have a time sheet that needs to record extra hours worked or time taken
off. I've got it all to work fine, except I can't get excel to recognise
deficit hours. For example, if a person works 7hrs of a 7.5 hour day, I
need
to show that they've had .5 hour off. Half hour chunks are the minimum
time
that anyone can record as extra work or take off as time owed.

Jason.