I have an Excel Spreadsheet that looks more or less like this:

```
+------------+-----------+
| First Name | Last Name |
+------------+-----------+
| John       | Paul      |
| Joe        | Jones     |
| John       | Paul      |
+------------+-----------+

```

What I need to be able to do is detect the amount of duplicate entries and show a number of rows where the first and last name were in there at least twice.

So basically I'm looking for how many people in the list were in the list at least twice.