In a previous article I explained how you can use Conditional Formatting in Excel 2007 and later to highlight duplicate values with just a couple of mouse-clicks. Although easy to implement, this technique identifies all instances of a duplicate value. A reader then asked how to format only the second and any subsequent instances. In this article I'll explain how, along with instructions on identifying duplicate values in Excel 2003 and earlier.
Figure 1: Conditional Formatting can identify the second and subsequent instances of duplicate values.
Let's say that we have a list of names, such as shown in Figure 1. Our goal is to highlight the second and any subsequent times that a name appears more than once on a list. To do so, we'll select the names, and then carry out these steps: