Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

procedure TForm1.Button1Click(Sender: TObject);
 var
   LoopAborted: Boolean;
   i: Integer;
 begin
   LoopAborted := False;
   i := 0;
   repeat
     // Your Code... 
    Caption := IntToStr(i);
     Application.ProcessMessages;

     if GetKeyState(VK_Escape) and 128 = 128 then
     begin
       LoopAborted := True;
       Break;
     end;

     Inc(i);
   until i = 100000;
   if LoopAborted then
     ShowMessage('User has aborted the loop!');
 end;