"Bob" wrote...
How do I tell the function to look in the first or second column?

Your original formula was

=IF(ISERROR(INDEX($R$9:$S$3094,MATCH(AV44,$S$9:$S$ 3094,FALSE),1)),
"",INDEX($R$9:$S$3094,MATCH(AV44,$S$9:$S$3094,FALS E),1))

Change it to the array formula

=INDEX($R$9:$S$3094,MATCH(MIN(ABS($S$9:$S$3094-AV44)),
ABS($S$9:$S$3094-AV44),0),1)