Add Check Box in Calender Control

Partial Class SelectWeekEnds
    Inherits System.Web.UI.Page

    Protected Sub Calendar1_DayRender(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DayRenderEventArgs) Handles Calendar1.DayRender
        Dim ctl As New CheckBox
        ctl.ID = "chk" & e.Day.Date.ToString.Substring(0, 10)
        e.Cell.Controls.Add(ctl)
    End Sub

End Class