I'm having a weird issue if anyone can help, I have a spreadsheet with various rows of data and at the end of each one I want to add a total column. (Sounds simple enough, and probably the first thing anyone learns on excel)

I'm using the basic =SUM(select row cells) and I'm getting 0 in the cell when there are clearly numbers to add up. It is also displaying a blue arrow, I have been into the formulas tab and selected remove arrows but whether it's there or not (although I have never had one show up before) the 'total' column SUM cells are just refusing to change from zero. If I retry the blue arrow reappears again no matter how many times I select remove arrows.

I have never encountered this before and feel a bit silly asking for help on such a basic function but as it's so basic I'm struggling to find an alternate way to just add up the values in the cells.

I'm using Excel 2007.