public void runCalculatorDialog(MouseEvent e) {
    if (calculatorDialog == null) {
      JFrame frame = null;
      Container container = getTopLevelAncestor();

      if (container instanceof JFrame) {
        frame = (JFrame) container;
      }

      calculatorDialog = new JDialog(frame, "Rechner", true);
      calculator = new Calculator();
      calculator.getOKButton().addActionListener(this);
      calculatorDialog.getContentPane().add(calculator);
      calculatorDialog.pack();
    }

    // Set calculator's init value

    Money money = getValue();

    if (money != null) {
      calculator.setValue(money.getValue());
    } else {
      calculator.setValue(0.0);
    }

    // calculate POP (point of presentation)

    Point point = ((JComponent) e.getSource()).getLocationOnScreen();
    int x = point.x + e.getX();
    int y = point.y + e.getY();

    // ensure that it does not exceed the screen limits

    Dimension screenDim = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension dim = calculatorDialog.getPreferredSize();
    if (x + dim.width >= screenDim.width) {
      x = screenDim.width - dim.width - 1;
    }
    if (y + dim.height >= screenDim.height) {
      y = screenDim.height - dim.height - 1;
    }

    // make it visible at wanted location

    calculatorDialog.setLocation(x, y);
    calculatorDialog.show();
  }