It is interesting, actually.

I have learned a lot at this site - including being able to answer your question, so I understand your curiosity!

=IF() statements are of the format, IF(some logic test, answer if the test is true, answer if the test is false)

The first part of this formula, the ISNA is the test that the IF is running - is the subsequent Index/Match test returning an #N/A?

The (INDEX('Unassigned Orders'!A

,MATCH(A4,'Unassigned Orders'!A:A,0),2)),"MISSING"

checks to compare A4 against the following: 'Unassigned Orders'!A:A,0 - in other words, is whatever is in A4 also in column A of the other sheet. It also looks at the array of A

. The reason for this is so, at the end, the number 2 tells what column matching a find to display, counting from the left. So in this formula it will display the first name. The 0 after the A:A (sometimes you will see FALSE instead) tells it only to show exact matches. Without that, it would show MISSING until it found a match, then show the first match until it found the next match, then show that match until it found the next and so on. So in the file I uploaded, you would have 2 MISSING, then Joe, then 11 more Joes, then Mark....

Because the IF test is to see if the ISNA is true - and that is based on whether or not there is a match, the answer if it is is MISSING. (It could easily have been anything else, from "" to 0 to "Tough Luck!".)

If it is not true, then the answer is to show the match - hence the repeated portion, apparently, of INDEX('Unassigned Orders'!A

,MATCH(A4,'Unassigned Orders'!A:A,0),2))

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