I do not have a ready example.  But here is basically the procedure.  Have a formula in the sub-report that assigns the total to a shared variable.  Then in the the main report have another formula that has the same same shared variable defined and put that formula in some section following the section the sub-report is in.  See the following

In sub-report
Not sure if you just need a number or currency.  Also not sure how the total is defined.
shared numbervar somevariable := total;

In Main report

shared numbervar somevariable;