Previous Year set

[Newbie777]

Hello,

I'd like to write a set sum expression where the chart always shows 1 year previous to the selected year.  I want to have the multi year chart so the expression below does not work 

Sum({$<[Date-Posting Date.autoCalendar.Year] = {$(=Year(Today())-1)}>}[Expenses])

where the chart will be limited to 1 year only which is previous year to the current year.  

I want to have the chart for multi year, which the current year shows the previous year YTD figure, then I can apply current year minus previous year to get the YOY difference.  

I'd greatly appreciate if someone can let me know how to write multi year previous year set expression.  

Thank you for your help.