Adding data from previous column in pivot table

[vpanchuda]

HI Experts

The Category and month are my dimension and Count of Category is the measure below is the table i got after calculation and Pivoting.

	MonthYear
Category	Totals	May-19	Jun-19	Jul-19	Aug-19	Jun-20
B1	4	-	3	1	-	-
B2	4	1	-	3	-	-
B3	1	-	-	-	-	1
C1	1	-	-	-	-	-
D1	2	-	-	-	-	-

I need the below calculation as in the table 

Category	Totals	May-19	Jun-19	Jul-19	Aug-19	Jun-20
B1	4	(Show the Pevious column if Null in this case 4)	3	1	-	-
B2	4	1 (Subtract with previous column if there is a value in this case 4-1=3)	-	3	-	-
B3	1	-	-	-	-	1
C1	1	-	-	-	-	-
D1	2	-	-	-	-	-

and the result table i intend to get should be like below.

	MonthYear
Category	Totals	May-19	Jun-19	Jul-19	Aug-19	Jun-20
B1	4	4	1	0	0	0
B2	4	3	3	0	0	0
B3	1	1	1	1	1	0
C1	1	1	1	1	1	1
D1	2	2	2	2	2	2

Can someone help me, please.