[dec]

Hola,

Código Delphi [-]
procedure CloseApplication(WindowTitle: string);
var
  winHandle: THandle;
begin
  winHandle := FindWindow(nil, PChar(WindowTitle));
  if (winHandle <> 0) then begin
    SendMessage(winHandle, WM_CLOSE, 0, 0);
  end;
end;

Un ejemplo de uso:

Código Delphi [-]
procedure TForm1.Button1Click(Sender: TObject);
begin
  CloseApplication('Calculadora');
end;