standard deviation

Hey,
I have got an Excel worksheet with a lot of stock prices.
I have to calculate the return, the expected return and the standard deviation.
For the expected return and the standard deviation i need to cover 60 days out of 1200 days and have to move on the window - so i start from day 1 to day 60, my next value is 2 to day 61 etc.
My expected return code works, but my standard deviation does not work properly...do you have any ideas for an improvement?

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