Get previous Month sales in straight table

[#1]

Hi everyone,

I need some help to get the previous month sales (not using Above function) in a straight table, even in the case there were no sales.

For example I have the following table:

AccountID	YYYYMM	YYYYMM_Prev	Sales
123	201501	201412	6536
123	201503	201502	800
123	201504	201503	4743
123	201510	201509	120
452	201512	201511	790
562	201410	201409	5464
562	201501	201412	7808

I need to see for :

Account 123, YYYYMM 201501, Sales Previous Month would be 0    (for Dec 2014)

Account 123, YYYYMM 201503, Sales Previous Month would be 0     (for Feb 2015)

Account 123, YYYYMM 201504, Sales Previous Month would be 800      (for Mar 2015)

I tried something along the line of

=SUM( {<YYYYMM={"$(=YYYYMM_Prev)"} >} Sales )

but did not manage to make it work...

Can someone please help?

Application is attached

Thanks in advance!

Jon

[#2]

check below blog post.

Calculating rolling n-period totals, averages or other aggregations

[#3]

Hello and thanks for the link you provided.

Seems like the AsOf Table is the best solution the problem I illustrated, even with the case of 'missing' dates in the data set as in my case.

I would very much appreciate if you can modifying my application to include the AsOf structure as I never seen it implemented?

Also since in my case, I need to do calculation for each AccountID?

Thanks!