HLOOKUP(value,range,row[,approximate,as_index])
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 equivalence. 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. as_index returns the 0-based offset that matched rather than the value.