Accessing controls

I have a control called DundasChart.ascx where I specify a public property chartDate:
 
    public DateTime chartDate {
        get { return m_Date; }
        set { m_Date = value; }
    }


then on my aspx page I have this:
<form id="form1" runat="server">
    <asp:Panel ID="myPanel" runat="server">
                <CC:DundasChart runat="server" ID="ccDundasChart1" />
                <CC:DundasChart runat="server" ID="ccDundasChart2" />
                <CC:Dunda ...