Excel 2010 Tips and Tricks

114 Tip 49: Creating Custom Number Formats
Parts of a number format string
A custom format string enables you to specify different format codes for four categories of values:
positive numbers, negative numbers, zero values, and text. You do so by separating the
codes for each category with a semicolon. The codes are arranged in four sections, separated by
semicolons:
Positive format; Negative format; Zero format; Text format
The following general guidelines determine how many of these four sections you need to specify:
If your custom format string uses only one section, the format string applies to all values.
If you use two sections, the first section applies to positive values and zeros, and the second
section applies to negative values.
If you use three sections, the first section applies to positive values, the second section
applies to negative values, and the third section applies to zeros.
If you use all four sections, the last section applies to text stored in the cell.
The following example of a custom number format specifies a different format for each of these
types:
[Green]General;[Red]-General;[Black]General;[Blue]General
This example takes advantage of the fact that colors have special codes. A cell formatted with
this custom number format displays its contents in a different color, depending on the value.
When a cell is formatted with this custom number format, a positive number is green, a negative
number is red, a zero is black, and text is blue. By the way, using the Excel conditional formatting
feature is a much better way to apply color to cells based on their content.
When you create a custom number format, don’t overlook the Sample box in the
Number tab of the Format Cells dialog box. This box displays the value in the active
cell by using the format string in the Type field. Be sure to test your custom number
formats by using the following data: a positive value, a negative value, a zero value,
and text. Often, creating a custom number format takes several attempts. Each time
you edit a format string, it’s added to the list. When you finally get the correct format
string, open the Format Cells dialog box one more time and delete your previous
attempts.