Set Analysis not WorkingMon

[#1]

Hi

I'm trying to use a set analysis for Selecting the last month minus one of the data that is created in the system1.

I have the following fields:

     System     : indicated where the data comes from. In this case I want to consider only the data with the tag system1

     [ID Month|Year]     : Is a correlative number for add/substract months. i.e I need info from five months ago (1,2,3,4...)

     [Month|Year]:          : The name of the correlative number i.e. Dec-2014, Jan-2014, ....

=MaxString( {1<[System]={"system1"}, [ID Month|Year]={"$(=Max( {$<Month|Year=>}  [ID Month|Year])-1)"}>} [Month|Year] )

This works like a charm, but considers the data from all the systems:

=MaxString( {1< [ID Month|Year]={"$(=Max( {$<Month|Year=>}  [ID Month|Year])-1)"}>} [Month|Year] )

What am I doing wrong?

Help please

Thanks!!

[#2 · Accepted solution]

Finally I solved it with the following expression:

=MaxString( {1<[ID Mes|Ano]={"$(=Max( {$<[Sistema de Origen]={"EBI"}, Mes|Ano=>}  [ID Mes|Ano])-1)"}>} [Mes|Ano] )

Hope it Helps somebody