Check CheckBox inside inner Repeater from outer Repeater checked in Asp.Net

There are two CheckBoxes one is in outer Repeater and other is inside inner Repeater.

I would like to automatically check CheckBox of inner Repeater when checked the outer Repeater's CheckBox.

HTML Markup:

<asp:Repeater ID="repOuter" runat="server">
    <ItemTemplate>
        <asp:CheckBox ID="chkOuter" runat="server" 
             OnCheckedChanged="chkOuter_CheckedChanged" />

        <asp:Repeater ID="repInner" runat="server">
            <ItemTemplate>
                <asp:CheckBox ID="chkInner" runat="server" />
            </ItemTemplate>
        </asp:Repeater>

    </ItemTemplate>
</asp:Repeater>

Code-Behind

protected void chkOuter_CheckedChanged(object sender, EventArgs e)
{
    // can't have access to inner CheckBox placed inside Inner Repeater
    CheckBox innerCheckBox; // how?

    innerCheckBox.Checked = true; // want to check it
}