Calculating Market Volatility

[Jwow]

Hi All,

Here is my issue
1) I have monthly market data for a commodity
2) I want to calculate the annual volatility

Which according to few = STDEV ( LN (returns) * SQRT (?)
(wondering if it will be 12 or 252 since i have monthly data).

Anyhoo, here is the excel challenge.
I want to calculate this is in one cell without populating column for log normal returns.
Please let me know if any way if this can be achieved.

Thank you
Jishnu