[[enecumene]]

Hola, colocar esto en los eventos AfterDelete y AfterPost de tu dataset, debes adaptarlo a tu manera:

Código Delphi [-]
procedure TFReposicion.cdDetallesAfterDelete(DataSet: TDataSet);
Var
Suma: Double;
Campo: TField;
Begin
     Suma:=0;
     Try
        With cdDetalles Do Begin
             DisableControls;
             Campo := FieldByName('valor');
             First;
             While Not EoF Do Begin
                   Suma := Suma + Campo.AsFloat;
                   Next;
             End;
        End;
     Finally
        cdDetalles.EnableControls;
     End;
     dsCaja.DataSet.FieldByName('total').AsFloat := Suma;
end;

Saludos.