=MAX(L2-C2-"12:00",0)

and format as time,[h]:mm

--

HTH

Bob

"Steve M" wrote in message
...
Hi
I would like to calcualte the time over a permitted amount and display it
in
a cell.

Column C is the start time dd/mm/yy hh:mm and Column L is the finish time
dd/mm/yy hh:mm. The alloted time is 12 hours for the job and and need
column
M to show the amount of time used over the 12 hours.

Many Thanks.