**AutoSum**button.

To add up the total of expenses for January, you wouldn't have to type all those values again. Instead you could use a prewritten formula, called a **function**.

You could get the January total by selecting cell B7, then clicking **AutoSum** on the **Standard** toolbar. This enters the SUM function, which adds up all the values in a range of cells. To save time, use the function whenever you have more than a few values to add up, so that you don't have to type the formula.

Pressing ENTER displays the SUM function result 95.94 in cell B7. The formula =SUM(B3:B6) appears in the formula bar whenever cell B7 is selected.

B3:B6 is the information, called the **argument**, that tells the SUM function what to add. By using a **cell reference** (B3:B6) instead of the values in those cells, Excel can automatically update results if values change later on. The colon (:) in B3:B6 indicates a **cell range** in column B, rows 3 through 6. The parentheses are required to separate the argument from the function.

The next two lessons explain cell references and functions in more detail.