How to allow multiple Date Select and changes color in Calander using C#

Question

I have monthCalendarAdv1 monthly Calendar ..i want make a program in C# window form on this Calendar when user will click on particular date , the color of this date need to change . .and when user will click another date then old date keep highlight with other selected ..i have make a program but its only changes the color of only one date

if (checkBox1.Checked)
  {

  monthCalendarAdv1.Colors.Selection.BackColor = Color.Red;
  string a = monthCalendarAdv1.SelectedDate.ToString();
  MessageBox.Show(a);


  }

Any body can help me ?????????????