{ Work procedure }
  Function Calculate_One_Interval {(var loan_status : loan_rec)} : boolean;
  var s                : varying [40] of char;
      cs               : Dwt$Comp_String;
      actual_repayment : double;
      new_value        : double;
      insufficient     : boolean;

  begin
  { Make the repayment }
   .
   .
   .
  { Display the result }
  writev(s,interval_number:3,current_value:16:2,total_paid:11:2);
  Dwt$Latin1_String(s,cs);
  Dwt$List_Box_Add_Item(list_box, cs, 0);
  Dwt$List_Box_Set_Pos(list_box, interval_number);
  Xt$Free (cs);
  Calculate_One_Interval := (current_value <= 0.0) or insufficient;
  end;