Cummulative Sum Based on Same Rank Issues

[SarikaB]

Hello Team, 

I am trying to do a Cummulative Sales based on Rank

Here, is my 

Rank Measure=

mRank = RANKX(ALL(PostedSalesInvoiceLines[No],PostedSalesInvoiceLines[CustName]),[mTotalSales],,DESC,Dense)

Cummulative Sales Measure:

mCumSsales = CALCULATE ([mTotalSales],TOPN([mRank],ALL ( 'PostedSalesInvoiceLines' ),[mTotalSales]))

Cummulative sum is not happening during same ranks.

Kindly let me know how to resolve.

Regards,

Sarika

[wdx223_Daniel]

mCumSsales = VAR _rx=[mRank] RETURN CALCULATE ([mTotalSales],FILTER(ALL(PostedSalesInvoiceLines[No],PostedSalesInvoiceLines[CustName]),[mRank]<=_rx))