Create a running total sparkline using PowerPivot DAX and Excel

Got an interesting question today. The question was about creating sparklines for all the country's that shows a running total of sales for the last 12 months based on the year that I select from a slicer. I use the trick I blogged about before to work with sparklines and PowerPivot, I would recommend reading it for some background.

First I want to start by creating the sheet that I want to use as a report. On this sheet I start by creating the slicer that I want to use, In this case Calendaryear: