How to get an old information from my table

[abraham_paradac]

Hi Comunity, I have the follow problem:

I Use a Excel File to get contable information from a period, for example:

Month           Should         Have              Balance Currently month     Balance Previous Month

1                          500,0           300,0                         200,0                                                     0

2                          800,0           200,0                        600,0                                                 200

3                         100,0            150,0                         - 50,0                                                 600

I need to show this information on a Pivot Table..

When I use a "Normal" Table and get Previous Balance on an external Field with a Set Analisys its Works well.

My set analisys is this: 

If(GetSelectedCount(Month)>=1,if(Month=1, 0, sum({<Month1={$(=Max(Month)-1)}>} ([Should]-([Have])))))

But when  I used this form in a Pivot Table does not Work.

In this Case I decided use a Before Sentence  for get Previous Month . Its works  

Before(SUM([Should]-([Have])))  

But I have a Big problem... When I make a Filter by dimension for example Month This information disapears.

I didn't Know how can I do for use a Pivot Table With Filters Dimensions and Get Previous Balance.

I Need Help.

Thanks

[OmarBenSalem · Accepted solution]

Try useing this measure:

aggr(above(Sum({<Month>}[Balance Currently month])),Month)

result:

if I select Month 2 for example:

[abraham_paradac]

Thanks is all I need!

[abraham_paradac]

I Would like to know How can convert Months Number into Months Char like '1' "Jan", '2' "Feb", '3' "Mar". Because I used Month(MakeDate(Year,Month)) and It Doesn't Work.
Thanks!

[OmarBenSalem]

Try : 

=month( date#( Month,'M'))

And to make it even better : 

=Capitalize( Purgechar( month( date#( Month,'M')),'.'))

[abraham_paradac]

It's Correct my Friend but, when I proceed to convert and I select for example feb. the field 'Previous Balance' Is get in blank "disappeared". How Another idea?

[OmarBenSalem · Accepted solution]

Create this new field in the script : 

Capitalize( PurgeChar( month( date#( Month,'M')),'.')) as MonthName

and change ur expression from : 

aggr(above(Sum({<Month>}[Balance Currently month])),Month)

to

aggr(above(Sum({<Month,MonthName>}[Balance Currently month])),Month)

[abraham_paradac]

Look the image and you can understand that I say.

[OmarBenSalem]

Please... read my last answer carefully and u'll correct this; I have to go !