A volatile function is simply a function that will recalculate each time any action is performed in Excel, such as entering data, changing column widths, etc. (One of the few actions that will not trigger a recalculation of a volatile function is changing a cell's formatting, unless you do this via Paste Special... » Formats.)

Probably the most well-known of all volatile functions are the `TODAY`

and the `NOW`

functions. Because the `TODAY`

function returns the current date, and the `NOW`

function returns the current date and time, it is vital that both of them recalculate often. If you have a worksheet that contains many volatile functions, however, you could be forcing Excel to perform many unnecessary recalculations on a continuous basis. This problem can worsen when you have volatile functions nested within nonvolatile functions, as the formula as a whole will become volatile.

To see what we mean, assume you have a worksheet that is using the `TODAY`

function in a 20-column-by-500-row table. This will mean you have 10,000 volatile functions in your workbook when a single one could accomplish the same job.

Rather than nesting 10,000 `TODAY`

functions within each cell of your table, in most cases you can simply enter the `TODAY`

function into an out-of-the-way cell, name it

(or just use the cell identifier) or another applicable name, and then reference TodaysDate in all your functions.**TodaysDate**

A quick and easy way to do this is to select the entire table and then select Edit » Replace... to replace `TODAY( )`

with `TodaysDate`

in all your formulas.

You will now have one `TODAY`

function in place of the 10,000 you would have had otherwise.

As another example, say the first 500 rows of column B are filled with a relative formula such as `=TODAY( )-A1`

, and the first 500 rows of column A have different dates that are less than today's date. You are forcing Excel to recalculate the volatile `TODAY`

function 499 times more than necessary each time you do something in Excel! By placing the `TODAY`

function in any cell and naming the cell TodaysDate (or something similar), you can use `=`

`TodaysDate-A1`

. Now Excel needs to recalculate only the one occurrence of the `TODAY`

function, resulting in a much tidier performance hit.