report 33020840 is either part of the localised version you use (india, US, ... ?) or part of a nav addin (module). you can check that in the object's versionlist and in the documentation trigger.
you can add option fields in request page of report.
seems, that there already exist 2 global variables StartDate, EndDate.
if they are local variables in your code sample, then add 2 global variables of type Date to the report: GlStartDate, GlEndDate
then edit the report's request page
add, if needed at the top as 2. line a new group, name it options (like in many standard reports)
under this group line add 2 field lines
field line 1, sourceexpr=GlStartDate,name=StartDate,caption=StartDate
same with field line 2, use GlEndDate instead
press F9 to edit the code editor
add in onopenpage trigger:
GlStartDate := DMY2DATE(1,4,Year);
GlEndDate := DMY2DATE(31,3,Year+1) ;
when running the report, these values can be overwritten by different values, eg. month start/end date values
in your code sample replace
StartDate := DMY2DATE(1,4,Year);
EndDate := DMY2DATE(31,3,Year+1) ;
by
StartDate := GlStartDate;
EndDate := GlEndDate ;