Monthly sales comparison selected year vs last year

[YYIP54XnGbX7dvWmsI9UR5DXUuGlubpa]

I'm trying to show 2 lines in one linegraph. I would like to compare the selected years sales per month versus the precious year sales per month. Here i have a small sample of my data: 

Created	AmountFcExclVat
2/20/2015 1:55:35 PM	500
5/25/2015 2:33:15 PM	400
5/26/2016 5:42:16 PM	800

Showing one line with sales is no problem, I put in

Dimension: Created.autoCalendar.Month

Measure: Sum(AmountFCExclVat)
This gives me a line with monthly sales, which i can filter per year by using a filter.

What i want is the above linegraph with two lines, one line for the selected year and one line for the year previous to the selected year. What I've tried to show current year vs last year:

Dimension:
Created.autoCalendar.Month

Measure:
Sum({<Created.autoCalendar.Month= {$(=only(Created.autoCalendar.Month))}>}AmountFcExclVAT)

Sum({<Created.autoCalendar.Month= {$(=only(Created.autoCalendar.Month)-12)}>}AmountFcExclVAT)

[anat · Accepted solution]

use year field in set analysis:

current year expression  - Sum({<Year= {$(=only(year))}>}Sales)

previous year expression - Sum({<Year= {$(=only(year)-1)}>}Sales)