[amibroker] Average and Standard Deviation for all data

[pmxgs]

Hi,

 I would like to calculate the average and standard deviation for all the data 
available in an array.
 For example:

  calc1=C-ma(C,30);
   
   I would like now to calculate an average and std. dev. of calc1 which gets 
updated as new bars appears.
 This average and std. dev. include all the available data.

  I have tried MA(calc1,barssince(not(isnull(calc1)))); but it doesn't work.

Any suggestions?

thanks