How to calculate period of time

[#1]

I have been looking the Community to find a way wchich will solve my problem, but i didn't find;(

I found an expression and tried to adopt to my aplication

Sum ({$<[Sales area]={'<b.o.>','VSG','ESG','FRG','SzcESG'},YearMonth = {'>=((=Left(Min(YearMonth), 4)-1)&Right(Min(YearMonth),2))<=((=Left(Max(YearMonth),4)-1)&Right(Max(YearMonth),2)'}>} Value)/1000

I need to calcute value for the same time period but "Year-1". It wouldn't be problem if i Had only one year, but user can choice from sleection for example

200911

200912

201001

201002

[#2]

format for YearMonth is:

YYYYMM

[#3 · Accepted solution]

I found the solution

(((Sum ({$<[Sales area]={'<b.o.>','VSG','ESG','FRG','SzcESG'},YearMonth={">=$(=((Left(Min(YearMonth), 4)-1)&(Right(Min(YearMonth),2))))"}*{"<=$(=((Left(Max(YearMonth), 4)-1)&(Right(Max(YearMonth),2))))"}>} Value))))/1000