Qfyilyi

I wish to To return the Header from the last number in row B that >100 , but currently I only manage to get the first number that >100 which is "july", But the answer that I want is "Aug" please help...

This array formula (ctrl+shift+enter !) should do the trick:
{=INDEX($P$1:$AA$1,MAX(IF(P2:AA2>100,COLUMN(P2:AA2)-COLUMN(INDEX(P2:AA2,1,1))+1)))}

The way this works is the following (and you can follow this if you select a part in the formula bar in Excel and type F9 to see the intermediate result) :

• 
  COLUMN(P2:AA2)-COLUMN(INDEX(P2:AA2;1;1))+1 creates a very simple array withe the column numbers of your range result={1,2,3,4,5,6,7,8,9,10,11,12}
  


• The P2:AA2>100 also creates an array with TRUE/FALSE when the condition is met result={FALSE,FALSE,FALSE,FALSE,FALSE,FALSE,TRUE,TRUE,FALSE,FALSE,FALSE,FALSE}
  


• The IF combines both : result={FALSE,FALSE,FALSE,FALSE,FALSE,FALSE,7,8,FALSE,FALSE,FALSE,FALSE}
  


• With the MAX you select the largest value, which will be 8 in our case


• And with the INDEX you get then the 8th value of the range, which is Aug

So the trick is combining a matching condition with a simple sequential array with the same number of values as there are in your range.