Yes, this can be done by using shared variables.
Create a formula on your subreport to assign the total to a varibale i.e.
//@SubTotal
WhilePrintingRecords;
Shared NumberVar SRTotal := {TotalField};
Then this can be used in your main report and added to your main report total i.e.
//@GrandTotal
WhilePrintingRecords;
Shared NumberVar SRTotal;
{MainReportTotalField} + SRTotal
The grand totalformula will only work if it is placed ina section after/below the subreport section.
HTH
Gary Parker
MIS Data Analyst
Manchester, England