We have thousands of rows of data in the following format
| Name | Born On |
|:-----------|------------:|
| Tom | Jul 15 |
| Harry | Jul 15 |
| Katy | Oct 2 |
| Britney | Oct 2 |
| Miranda | Oct 2 |
| Victoria | Oct 2 |
| John | Sep 30 |
| Warren | Sep 30 |
| George | Sep 30 |
I would like to add a serial number based on the "Born On" column as follows
| Name | Born On | Serial Number
|:-----------|------------:|--------------:|
| Tom | Jul 15 | 1
| Harry | Jul 15 | 2
| Katy | Oct 2 | 1
| Britney | Oct 2 | 2
| Miranda | Oct 2 | 3
| Victoria | Oct 2 | 4
| John | Sep 30 | 1
| Warren | Sep 30 | 2
| George | Sep 30 | 3
The "serial number" needs to be grouped by "born on" date. Please help. Thanks.
If the serial numbers start in cell C2 and the Born on cells start in B2, then use this formula in cell C2 and copy down:
=COUNTIF(B$2:B2,B2)