Sets: An Introduction to Processing Set Theoretical Notation in Microsoft Excel®
Sets is an add-in that processes set expressions. If you're not familiar with set theory, most of the features won't be too exciting. If you don't need to evaluate set expressions, you won't need it. But, if you need to learn about set notation, read on. (If you're just interested in learning how VBA can be used for processing expressions, that's okay too.)
The Union operation between two sets gives the set of all elements in either one.
The intersection of two sets gives the set of all elements which they both have in common.
Sets.xla provides support for ordered sequences as set elements. This means that it does not try to remove duplicates from, or sort elements of, ordered sequences of elements.
Add-ins supply additional functionality to Excel® workbooks. Set processing is written with Visual Basic for Applications®(VBA). Add-ins remain in the background until they are needed. You can read all about them in Excel's Help documentation.