Ok. Thanks. I did find it and it is Date/Time. I did try the more simplistic calculation and it did not work either. It still gives me the same error message. I am using Formula (Date/Time). {custrecord_f4n_worked_hours_sales_order.custrecord_f4n_worked_hours_end_time} -{custrecord_f4n_worked_hours_sales_order.custrecord_f4n_worked_hours_start_time}. Any suggestions?