How to Display Current Month VS Previous Month column in Matrix?

Today i will explain how to display (currentmonth- Previous Month ) column in Matrix.

 i Have JAN to DEC column grouping and i want to display currentmonth -Previous Month column out of the group column.

Then

write Below expression

=SUM(iif(Fields!Month.Value = Month(now.Addmonths(- 1)), Fields!Orders.Value, Nothing)) 

- SUM(iif(Fields!Month.Value = now.Month, Fields!Orders.Value, Nothing))