Finding duplicates in one column based on unique values in another

Question

I have two columns of data, see below:

|---------------------|------------------|
|        Email        |       Number     |
|---------------------|------------------|
|        email1       |         1        |
|---------------------|------------------|
|        email1       |         2        |
|---------------------|------------------|
|        email1       |         3        |
|---------------------|------------------|
|        email2       |         1        |
|---------------------|------------------|
|        email2       |         2        |
|---------------------|------------------|
|        email2       |         2        |
|---------------------|------------------|

Can I somehow use conditional formatting to colour the cells where the number column has a duplicate for a unique email? In the table above, the last 2 rows should have their columns colour changed since the number 2 appears two times for the same email.

Thanks in advance!

Answer 1

This would be the formatting for A2:B7:

=SUM(($A2&$B2=$A$2:$A$7&$B$2:$B$7)*1)>1

I concatenate the A and B columnns and see how many rows match "this" row. The regular result should be 1 - higher values mean duplicates.