HLOOKUP function finds the col in range that has a first row cell similar to value. If @approximate is not true it finds the col with an exact equivilance. If @approximate is true, then the values must be sorted in order of ascending value for correct function; in this case it finds the col with value less than @value it returns the value in the col found at a 1 based offset in @row rows into the @range.
Returns #NUM! if @row < 0. Returns #REF! if @row falls outside @range.