First, if you select a cell containing a number and drag the AutoFill handle, Excel assumes you want to simply copy the value. When you release the mouse button, the AutoFill options button appears. Click the option for

**Fill Series**

to replace the multiple copies of the selected number with a series of numbers that increment (or decrement) by one.

Second, if you select two adjacent cells with distinct numerical values and drag the AutoFill handle, Excel fills the cells with a series which increments by the difference of the two values. In other words, if you selected one cell containing the number 1 and another cell containing the number 3 and then dragged with the AutoFill handle to the right, the resulting series would be 1, 3, 5, 7, etc. Each subsequent value would be 2 more than the last. In this way you can increment a series by twos, by threes, or even by twenty-sevens.

### Customizing Excel’s AutoFill List

As we have seen, Excel knows days, months, and numbers — and that’s it. If you select a cell with any other “non-series” data and drag the AutoFill handle, Excel just copies those cells. However, you can create your own custom list — or lists — to “teach” Excel new series.

Let’s teach Excel the first ten ordinal numbers, first through tenth. In Excel 2003, click

**Tools > Options > Custom Lists**

. Then select

**New List**

and type each list entry, separating the values with commas. Finally, click

**Add**

, then

**OK**

.