unit Unit2;

interface

uses
  Classes, StdCtrls, SysUtils;

type
  Generator = class(TThread)
  private
    { Private declarations }
  protected
    procedure updateMemo;
    procedure Execute; override;
  public
    list: TListBox;
  end;

implementation

uses Math;

procedure Generator.Execute;
var
  i: integer;
begin
  for i:=1 to 1000 do
  begin
     Synchronize(updateMemo);
  end;
end;

procedure Generator.updateMemo;
begin
  list.Items.Add(IntToStr(RandomRange(1, 100)));
end;

end.