value: search value
range: range to search
row: 1-based row offset indicating the return values
approximate: if false, an exact match of value must be found; defaults to TRUE
as_index: if true, the 0-based column offset is returned; defaults to FALSE
HLOOKUP function finds the row in range that has a first cell similar to value. If approximate is not true it finds the column with an exact equality. If approximate is true, it finds the last column with first value less than or equal to value. If as_index is true the 0-based column offset is returned.
If approximate is true, then the values must be sorted in order of ascending value. HLOOKUP returns #REF! if row falls outside range.