as Glenn noted posting a sample will go a long way toward getting the appropriate answer.
However from what I see in this formula =IF(ISNA(VLOOKUP(I$39,$L9:$S9,2,FALSE)),"",VLOOKUP(I$39,$L9:$S9,2,FALSE)) is that you are saying to look at the value in I39 and go to see if it is in L9 and if it is go over to M9 (the 2 part of the formula) and return that value. I don't know why you have it going from L9:S9 since anything past M9 is irrelevant to the formula - just a thought.