Cell validation and row highlighting

Hi,
I have a table with two columns, one for 'Desk number' and another for 'Employee name'. After editing a cell value, I would like to be able to check that no two rows in the table have the same desk number.
If two rows do have the same desk number, I would like to highlight those rows.

Is this possible, and if so, how may I achieve this?
If not, is it possible to do something similar?

Thank you