Cumulative sums of workload

[waszcma1]

Hi,

I have been asked to create line graph with information about workload 

Business asked me to create cumulative sum which is no problem (see table second column)

But additional to that I have drop numbers for RFC which go-Live date is passed

i.e.:
we have created
2022-01  18 RFC (most of RFC have go live after 5-6 month but 2 of them have go live on 2022-02)
2022-02  9 RFC ( all of RFC have go live after 5-6 month)
2022-03  4 RFC ( all of RFC have go live after 5-6 month)

so I want to reported on 2022-03 (18-2)+9+4 = 29

Currently cumulative sum is not including the second conndition and returns  18+9+4=31 

Any Idea how to achieve this?