Returns a value from a list, given an index number.
CHOOSE(index, value1, value2, ... value30)
value1 ... value30 are up to 30 values, each of which may be text, a number, a logical value, a reference or a formula.
index is an index number specifying which of value1 ... value30 to return; 1 returns value1, 2 returns value2, etc.
CHOOSE(1, "dog", "cat")
returns the text dog.
CHOOSE(2, "dog", 65.4)
returns the number 65.4.
CHOOSE(3, "dog", 65.4, B5)
returns the reference B5, so that CHOOSE(3, "dog", 65.4, B5) in a cell shows the contents of cell B5 in that cell (it is equivalent to B5).
SUM(CHOOSE(1, B4:B5, B6))
returns the sum of the numbers in the range B4:B5.
CHOOSE(2, SUM(B1:C1), SQRT(9))
returns 3, the square root of 9.