stdev in pivot table, ?is this even possible? ?how?

[#1]

Hello,

I have a simple data table that has, among other things, the customer creation timestamp, and their "birth-decade", which has values in the range of 192 to 199 (most are 198, btw).

I have a fine pivot table, which has as dimensions Birth_Decade and WeekStart(cust_creation_time)

The expression CustAmt is merely count(customer_id)

So that works fine.

But then users want

A) calculate average count over past 18 1st business day of the week

B) calculate standard deviation of count over past 18 1st business day of the week

included in this pivot table. Here the hemorrhaging starts.

Tried <> syntax, AGGR, sets, nothing works.

?How can this be done?

[#2]

Btw, just to get me started, I'd be happy with just getting a stdev for each of the birth_decades over all the weeks -- the best I can get now is "0"