Bell Curve formula

[AsmJuv2004]

Hi All,

I watched the below video to create a bell curve. 

https://www.youtube.com/watch?v=q2QHhtvzbDc

I used the expression as suggested in the bell curve.

Only(Normdist(Round(original_val,0.1),Avg(total original_val),Stdev(total original_val),0))*0.1*Count(total original_val)

I need to create another bell curve with a different standard deviation which is calculated using the below formula. please help in writing the expression.

sum(aggr( fabs(above(sum(original_val)) - sum(original_val)) ,Product,characteristic_desc_txt,([Record Time], Numeric, Descending) ))
/
(Aggr(count(original_val),Product,characteristic_desc_txt)-2+1)