Delphi Team: Show way with running total and calculated fields

Hello everybody,
I have running total with my tables/Queries. My understanding of running
total is total of
a particular field for all the records present in the DataSet.
I have kept them separate from the front-end (even TDataSource). So a TQuery
by itself
manipulates the running total. Something on the lines of Business Objects.
Any front-end designer then would access this running total. But this
running total is available
as a variable. In what way can I inform front-end control (eg. Tlabel, etc.)
that now it should
show the value of running total variable again ?
Otherwise I am thinking of putting a calculated field in the DataSet and
assign value of
running total variable to this field in ( OnCalcFields). Having a field per
record is not a
problem as I can make sure value accessed at each record is the same running
total variable.
The problem is 'OnCalcFields' is fired even otherwise ( AutoCalcfields set
to False does not
help me at all).
As I know particular event from where running total variable is updated. I
would like to trigger
an event (my own) from these events (from where running total variable is
updated). I can
achieve the above mentioned part but I can't change the value of calculated
field from outside
OnCalcFields.
When I probe around in Delphi source code I find out that in DB.Pas file,
procedure TDataSet.GetCalcFields(Buffer: PChar);
var
  SaveState: TDataSetState;
begin
  if (FCalcFieldsSize > 0) or FInternalCalcFields then
  begin
SaveState := FState;
FState := dsCalcFields;
try
   CalculateFields(Buffer);
     finally
   FState := SaveState;
end;
  end;
end;
The problem is from outside (DB.pas file) I can't access FState and State is
declared as readonly in this file.
How do I solve above problem ?