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