Is there a Dax or Var formula to sum across rows for 3,6,9 months?

[checkstatap]

Hi All, 

I am trying to find a solution to add columns that sum across rows for customers as in the example below:

[checkstatap]

@saurabhtd what format should the folling be?       'Table'[Month]

[saurabhtd]

@checkstatap You can try these formulas for creating calculated column. 

Last 3 Months = 
VAR CurrentMonth = MAX(Table[Month])
RETURN
CALCULATE(
    SUM(Table[Revenue]),
    FILTER(
        Table,
        Table[Customer] = EARLIER(Table[Customer]) &&
        Table[Month] >= CurrentMonth - 2
    )
)

Last 6 Months = 
VAR CurrentMonth = MAX(Table[Month])
RETURN
CALCULATE(
    SUM(Table[Revenue]),
    FILTER(
        Table,
        Table[Customer] = EARLIER(Table[Customer]) &&
        Table[Month] >= CurrentMonth - 5
    )
)

Last 9 Months = 
VAR CurrentMonth = MAX(Table[Month])
RETURN
CALCULATE(
    SUM(Table[Revenue]),
    FILTER(
        Table,
        Table[Customer] = EARLIER(Table[Customer]) &&
        Table[Month] >= CurrentMonth - 8
    )
)

[checkstatap]

Is it possible to add a if statement here as well? So if 0 revenue, then "Lost Customer"