Delphi7 — ошибка variable required при использовании CreateThread — как исправить?

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    TrackBar1: TTrackBar;
    TrackBar2: TTrackBar;
    Timer1: TTimer;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Edit1: TEdit;
    Edit2: TEdit;
    Button3: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
    procedure TrackBar2Change(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure Execute1(Sender: TObject);
    procedure Execute2(Sender: TObject);
    procedure Button3Click(Sender: TObject);

  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  Count1,Count2: integer;       {число вычислений в секунду в потоке}
  ThreadId1,ThreadId2: dword;   {идентификатор потока}
  HThread1, HThread2: THandle;  {указатель на поток}
      
implementation
{$R *.dfm}

    procedure TForm1.Button1Click;
      begin
         HThread1:=CreateThread (nil,0,@Execute1,nil,0,ThreadId1);
      end;

    procedure TForm1.Button2Click;
      begin
         HThread2:=CreateThread (nil,0,@Execute2,nil,0,ThreadId2);
      end;

    procedure TForm1.TrackBar1Change(Sender: TObject);
      begin
         SetThreadPriority(HThread1,TrackBar1.Position);
      end;

    procedure TForm1.TrackBar2Change(Sender: TObject);
      begin
        SetThreadPriority(HThread2,TrackBar2.Position);
      end;

    procedure TForm1.Timer1Timer(Sender: TObject);
      begin
        form1.Edit1.Text:=intTostr(Count1);  Count1:=0;
        form1.Edit2.Text:=intToStr(Count2);  Count2:=0;
      end;

    procedure TForm1.Execute1(Sender: TObject);
      var
        I, Total, Avg: integer;
      begin
        while True do
          begin
            Total:=0;
            for i:=1 to 10 do inc(Total, Random(Maxint));
            Avg:=Avg Div 10; inc(Count1);
          end;
      end;

    procedure TForm1.Execute2(Sender: TObject);
      var
        I, Total, Avg: integer;
      begin
        while True do
          begin
            Total:=0;
            for i:=1 to 10 do inc(Total, Random(Maxint));
            Avg:=Avg Div 10; inc(Count2);
          end;
      end;

    procedure TForm1.Button3Click(Sender: TObject);
      begin
        close;
      end;

end.