Update, just realised that the range to looked at could be more than one column wide, so new CF formula:
Code:
=AND(ISNUMBER(SEARCH($C$2,B4)),ISNUMBER(MATCH(ROW(B4),ROW(INDIRECT($A$2 & ":" & $B$2)),0)),ISNUMBER(MATCH(COLUMN(B4),COLUMN(INDIRECT($A$2 & ":" & $B$2)),0)))
See attachment.