Say your codes are in A2:Z2....and your dates are in A3:Z3....

try:

=SUMPRODUCT(--($A$2:$Z$2<>A2),--($A$3:$Z$3=A3)) copied to the right...

If you have a result of 1 or more, then the date is repeated for opposite code...if you have a result of 0, then the "other" code does not appear for same date within range....

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