Spreadsheets are used to store data, they are also used to make calculations. When you enter a formula into a spreadsheet, the best way to make a formula is to use a cell reference. Using a cell reference allows you to change the data and Excel will recalculate for you without having to change the formula.
Let me know if you need exact information on how to write a formula, but using a cell reference in a formula will look like this
=A1+A2+A3+A4 instead of =2+5+7+9
Excel has a Sigma button - which simplifies making a formula for working with numbers. With OpenOffice, the autosum is still the Sigma sign, but you don't see it until you are in the formula bar.
