I'm working on a time sheet where employees work a max of 80 hours in a two week period. Once they reach 80 hours, then OT kicks in. So, I'm trying to do the calculation for the OT...and created this formula =IF((N28-80)<80,SUM(N28-80),0) - which works great if they have 80 or more hours, but if less than 80, I'm getting a negative value in the field. What did I do wrong?