I've got a multi worksheet book analyzing monthly costs and sales for a restaurant. I entered the numbers for last month and the SUM function didn't work. The formula was already there, it just didn't tally the data. In other pages, same problem - according to the formulas in the blank cells, I should have data, but I don't. The only way I found to update the cells was to click inside the formula bar for each cell and press enter. Like I said, the formulas are already in place.
Furthermore, if I re-enter the formula and then drag the handle down to where I want my relative formulas, both the original value AND the relative formulas appear. Is this a virus or something??

Thanks for any help.