User enters any array of numbers beginning in any cell: Example

A15 23
A16 11
A17 5
. .
. .
. .
A172 145
A173 220


Required: Formula (not VBA, but perhaps array-entered) which will:

1) return a RANDOM number from AMONG the items in the list
2) Not require that the list start, list end, or # of items in the
list be fixed (only col A is fixed).
3) not require that the list be in ascending or descending order
3) be entered in cell B1

I started something involving INDEX and the ROW() of the starting and ending
item, but I want it to be more dynamic. Then I tried to use MATCH to tell me
the start or end values, by using 0.001 and 1,000,000 and matching with
Match_Type = 1, or -1, but that required the items be in ascending or
descending order. So, I am stuck... can it be done?