The index or offset arguments for all of the lookup
functions start at 1 (Lotus 123 functions start at 0).

CHOOSE(index,expr1,expr2 ... exprn): Selects an item from
   the list of expressions at position given by index.

INDEX(row offset,column offset,range): Returns the value of
   the cell located by the row and column offsets within
   the indicated range.

MATCH(compare value,range,type): Returns the position within
   the range of a cell matching the compare value.
   Type =  1: Greatest number <= compare value
   Type =  0: Exact match
   Type = -1: Smallest number >= compare value
LOOKUP(compare value,lookup range,results range): Searches
   the lookup range for the greatest value <= the compare
   value and returns the value of the cell at the same
   relative position within the results range.

HLOOKUP(compare value,row index,range): Horizontal lookup.

VLOOKUP(compare value,column index,range): Vertical lookup.

Both HLOOKUP and VLOOKUP search for the greatest value <=
the compare value and use index as an offset into the range.
For example, if cell A2 contains 2, VLOOKUP(1.5,2,A1:B3)
could match this cell, and it would return the value of cell
B2, since the column index was 2.

