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I don't know if this can be of any use but:

=INDEX(C3:L3,N(IF(1,MATCH({1,2,3,4,5};INT(C4:L4/600);0)))) (array formula)

will return an array with your wanted result. The cell will only show YR2, but try to select the cell with the formula, then press F2 and afterwards press F9.