I'll try your suggestion of putting formulas on a separate sheet but I'm not sure how I can get away with not using a macro. The data sheet has only a previous mileage column and a current mileage column, it doesn't have mileage for each month. And the end-user will not allow changes to the data sheet as far as what data goes in which columns. Maybe I'm not understanding your solution. Thank you anyway for your help. You've given me some things to think about.