find control on control ? (Web User Control)

I have this code
protected void btnEdit_Click(object sender, EventArgs e)
    {
        int x = 0;
        for (int i = 0; i < PanelGroupList.Controls.Count; i++)
        {
            if (PanelGroupList.Controls[i].GetType().ToString().Equals("GroupListControl"))
            {
                GroupListControl con = (GroupListControl)PanelGroupList.Controls[i];

                CheckBox test = (CheckBox)con.FindControl("cbSelect");

                Debug ...