sir,

i tried to make a dummy table to try the formula you gave me, however,
it returns the wrong header. when i search for 150, it returns header
"sub3" instead of "sub2".i wonder what seems to be the problem?

sub1 sub2 sub3
1 158 2
3 146 6
5 197 8
100 150 10
121 136 11
130 147 9
56 12 21
14 35 26
19 36 28

{=INDEX(A1:C1,MATCH(TRUE,COUNTIF(OFFSET(A2:C10,,CO LUMN(A2:C10)-COLUMN(A2),1),E2)0,0))}