Find duplicate values with select tow dropdown list

Hi all,

I have four columns and I have some dropdown list

I want that when I have select tow or some cells which have data into the dropdown list, I can find duplicates values

Please, without VBA & helper column

Thanks a lotone1.gif

Very long Array formula for Excel 2010
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Shorter one

Formula:

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Formula:

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Easier with MS365

=LET(a,FILTERXML("<x><m>"&TEXTJOIN("</m><m>",,IF(COUNTIF($F$2:$F$5,A1:D1),$A$2:$D$5,""))&"</m></x>","//m"),UNIQUE(FILTER(a,ISNA(MATCH(a,UNIQUE(a,,1),)))))

Thank you so much!