Finding & Highlighting Duplicate Names over a range of dates

[SueHopson]

Date    Detail Summary    Ref 1    Ref 2    Ref 3    Ref 4    Ref 5
24-Nov    RMC     XX Other    Sue B    Martin    Khanyiso    Sue L
25-Nov    RMC    Sue B    XX Other    Martin    Conrad    Charles
 25-Nov    OVA    Sue B                
26-Nov    OVA                     
29-Nov    STMARY Catholic Cup    Dianne    Conrad            
1-Dec    NDSS Sr Girls    Amanda    Dale    Ted    Debbie    

Hi everyone,

I have been able to find bits and pieces by searching various forums and websites, but am unable to find a way to combine what I am trying to do. So here I am, asking the pros once again.

I need to know if there is a way to highlight only the duplicate name the second time Sue B appears on Nov 25. The goal here is to validate that no person is assigned more than once on the same day, and if they are, to highlight them on any second and subsequent appearances on that same date. I am (unfortunately) using Google sheets, which my end-users are familiar with so that may affect your responses.

As always, any help is greatly appreciated.