ArrayList myList = new ArrayList();
            int firstNumber=int.Parse(txt1.Text);
            int secondNumber = int.Parse(txt2.Text);
            for (int i = firstNumber; i <= secondNumber; i++)
            {
                if (i%2==0)
                {
                     myList.Add(i);
                     lstbox1.Items.Add(myList);

                }
            }