Slicer value -1

[JGL]

I have a measure to calculate a productivity value based on slicer called week. I would like to have another measure to calculate same productivity but with value based on week -1. 

[rautaniket0077]

previousweekproductivity = 

var a = SELECTEDVALUE('Date'[Week])

var b =

CALCULATE(

    SUM(Orders[Sales]),

        'Date'[Week] = a-1

)

return b

put the column inside selectedvalue in slicer.

if it solves your issue accept my answer as solution.