Create a shared variable for passing data from subreport to main report

Since CR not allowed to sum (formula), e,g, sum({@mainformula), I
calcualte the grand total from subreport. detailed steps are:

1. In subreport, create formula called subformula, the shared valiable = grand total

WhilePrintingRecords;
Shared CurrencyVar myTotal :=Sum ({Command.SUM(AB.FEEAMOUNT)})

2. In main report, created a formula called mainformula

WhilePrintingRecords;
Shared CurrencyVar myTotal;
myTotal

3. Then put this mainformula on the main report underneath of subreport. Here what you want for the result.