Show variation to previous month in a Line Graph with month dimension

[#1]

Hi,

I have a Line graph with monthly evolution sales (blue line) showing last year same month sales (red).

I want to show as a new expression sales of previous month (for the range of months in the selection).

My expressions are:

-USD =Sum(dolares)

-USD (-1 Year) =Sum({$<year={$(=Max(year)-1)}>}dolares)

-USD (-1 Month) =Sum({$<month={$(=Max(month)-1)}>}dolares)

In the graph I get a green point, that I want to be a line and I want to shift 1 month forward.

Any suggestions?

Thanks in advance.

Javier