Cumulative to Non-Cumulative Totals - DAX Assistance Needed

[Anonymous]

Hello all! I've got a data set with cumulative amounts. I'm trying to calculate the non-cumulative monthly totals using DAX . How can I get PowerBI to identify total amount as of today and subtract total amount from last month? 

Let me know if you need any more info. Thanks in advance!

Current Data Setup:

MonthName	FiscalMonthInt	Amount (Cumulative)
OCT	01	67,904,161
NOV	02	16,1620,357
DEC	03	322,803,193
JAN	04	488,696,422
FEB	05	714,247,442
MAR	06	966,124,818
APR	07	1,133,638,748
MAY	08	1,407,021,012
JUN	09	1,518,0556,75
JUL	10	0
AUG	11	0
SEP	12	0

I'd like to create a DAX measure that creates a non-cumulative column.

MonthName	FiscalMonthInt	Amount (Cumulative)	Amount (Non-cumulative)
OCT	01	67,904,161	67,904,161
NOV	02	161,620,357	93,716,196
DEC	03	322,803,193	161,182,836
JAN	04	488,696,422	165,893,229
FEB	05	714,247,442	225,551,020
MAR	06	966,124,818	251,877,376
APR	07	1,133,638,748	167,513,930
MAY	08	1,407,021,012	273,382,264
JUN	09	1,518,0556,75	111,034,663
JUL	10	0	0
AUG	11	0	0
SEP	12	0	0

Seems simple but I can't figure it out. Thanks all.

[Jos_Woolley · Accepted solution]

Hi,

MyMeasure =
VAR ThisMonthInt =
    MIN( 'Table'[FiscalMonthInt] )
VAR PreviousMonthInt = ThisMonthInt - 1
VAR ThisAmount =
    MIN( 'Table'[Amount (Cumulative)] )
VAR PreviousAmount =
    CALCULATE(
        MIN( 'Table'[Amount (Cumulative)] ),
        FILTER( ALLSELECTED( 'Table' ), 'Table'[FiscalMonthInt] = PreviousMonthInt )
    )
RETURN
    IF( ThisAmount = 0, 0, ThisAmount - PreviousAmount )

Regards