Rangesum of column (Month) and row (Year) in a pivot table

[Newbie777]

Hello,

I'd like to write a rangesum formula in order to sum up both column and rows in the pivot table like below, which is only currently summing up columns.  

I'd appreciate it if you could let me know how I can modify the measure expression below (especially the yellow highlighted syntax) in order to achieve the cumulative sum of year and month.  

Thank you & best regards,