Passing value between sub report and Main report

In sub report I have accumulating formula in detail line with shared variable, I concatenate  values from this field and then I want to  pass that value in main report . When I check value of formula on detail line is showing right value.
But when I pass shared variable in main report it show last value from sub report detail line twice?
(Sub report is running in main report in section above where shared variable is used.)
I assume that is something with re setting shared variable but not sure I tried to re set it in sub report Header the same, in sub report GH2 not good It show empty in main report.


I have two grouping in Sub report  G1 Student ID  this is connecting field between Main and sub report.
Next Group is Activity Type and then detail line.

So I have something like this.

RH
GH1(StudentID)-----
WhilePrintingRecords;
Shared StringVar DescAcum:="";

GH2(ActivityType)
DL-Here is formula------
WhilePrintingRecords;
Shared StringVar DescAcum;
If {tableA.ActivityType} = "Soccer"  And  {?Semester} = "1" And Month ({TableA.Dateto})= 1.00 then
DescAcum:= DescAcum + {TableA.Description} + ";  ";