Hello Tmbutter,
You can use this Excel formula in F5 to return TRUE or FALSE based on whether the lookup value exists:
=IF(COUNTIF(INDEX(A3:C6,0,MATCH(F3,A2:C2,0)),F4)>0,TRUE,FALSE)
Explanation:
MATCH(F3, A2:C2, 0): Finds the column number of the selected header in F3.
INDEX(A3:C6, 0...