previous month sales

[#1]

this is current month MTD but i want last month sales not last month MTD

(((sum({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(MonthEnd(max(DateNum))))"}>}BILLDETAILAMOUNT)

-

SUM({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(=MonthEnd(max(DateNum))))"}>}BILLDISCOUNT))

-

(sum({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(=MonthEnd(max(DateNum))))"}>}BILLDETAILAMOUNT))

-

(sum({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(=MonthEnd(max(DateNum))))"}>}BILLDETAILAMOUNT))

+

SUM({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(=MonthEnd(max(DateNum))))"}>}BILLDETAILOTHERSTONECHARGE)

-

SUM({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(=MonthEnd(max(DateNum))))"}>}BILLDETAILOTHERSTONECHARGE)

-

SUM({<SalesFy=,Quarter=,Month=,Week=,BILLDATE=,DateNum={">=$(=Num(MonthStart(Max(DateNum))))<=$(=num(=MonthEnd(max(DateNum))))"}>}BILLDETAILOTHERSTONECHARGE))

)/(AmtFlag)