standard deviation excluding outliers

hi all,

i have a range of numbers in C5:AL5
Not all of the cells are filled in, and some that are filled in are blank.

In AM5 I calculate the average of the data
and in AN5 the standard deviation where the value in the cells in the range are >0

Is it possible to calculate a standard deviation in another cell which excludes those values in the range which are 3 standard deviations away from the value in cell AN5.
Therefore, the standard deviation with the outliers.

If there is another way of doing this, i would be grateful for your help.
Luce