How to find the mismatched variable where variables should all match

[tanya_henderson]

I am creating a report for error checking data entry. I have multiple columns where the dates should all match  to reflect that each assessment was completed on the same day. I am trying to create a report that will highlight "Which of these things is not like the others". 

I am currently highlighting all of the visits where the dates do not match, but I would like to be able to highlight only the fields that are dissimilar to the others. 

Here is my current code in my proc report data step. 

compute date4;
if date1 ne date2 or date2 ne date3 or date3 ne date4 then do;
call define("date1", 'style', 'style=[foreground=red font_weight=bold]');
call define("date2", 'style', 'style=[foreground=red font_weight=bold]');
call define("date3", 'style', 'style=[foreground=red font_weight=bold]');
call define("date4", 'style', 'style=[foreground=red font_weight=bold]');
end;

endcomp;

[mkeintz]

If you have 4 dates, with values      15OCT2019, 15OCT2019,  07OCT2019, and 07OCT2019, what is your rule for identifying which one(s) is/are different?   Sure, if you have 3 identical and 1 non-identical, it's obvious,  but what if you have 2 pairs as per my question.  Or what if you have 4 distinct dates?

So what are you desired rules of identification?

[tanya_henderson]

I do have one column that is the preferred standard to compare to but sometimes that is the odd date. So, I guess I could compare all dates to date1 and highlight the differences unless all dates are the same and date1 is the odd date.