I checked the cell format and it is General, not Text. I also tried formatting it as Number. Neither changed the outcome; the formula still appears in the cell. I also hit F2 and then enter and again no change. There does not appear to be a space before the = in the formula bar. When I click on fx, the correct sum appears in the function box, but when I click on "OK", the formula still appears in the cell. This is just a simple column of numbers (wedding invitees), and my Excel on my office machine produces the number, so this is quite frustrating!