Custom form control with multiple fields

I've created a custom form control for use with a document type. It contains two fields: a dropdown of available meetings, and a checkboxlist that populates with a list of sessions when a meeting is selected.

Everything is working fine as far as the display and writing back to both fields in the database when a user submits a form. The one thing I'm having trouble with is having the fields populate with the previously saved information when a user returns to the form. The dropdown populates correctly, but not the checkbox list.

.ascx code:

<cms:CMSUpdatePanel ID="pnlUpdate" runat="server" ChildrenAsTriggers="true">
<ContentTemplate>
    <asp:DropDownList ID="ddMtg" runat="server" OnSelectedIndexChanged="ddMtg_SelectedIndexChanged" AutoPostBack="true" CssClass="form-control"></asp:DropDownList>

    <asp:CheckBoxList ID="cblFunctions" runat="server" CssClass="checkbox checkbox-list-vertical"></asp:CheckBoxList>
</ContentTemplate>

<Triggers>
    <asp:AsyncPostbackTrigger ControlID="ddMtg" EventName="SelectedIndexChanged" />
</Triggers>
</cms:CMSUpdatePanel>

.cs code:

protected string connectionString = ConfigurationManager.ConnectionStrings["DataSource.iMIS.Connection"].ConnectionString;

/// <summary>
/// Gets or sets the value entered into the field
/// </summary>
public override object Value
{
    get
    {
        return ddMtg.SelectedValue;
    }
    set
    {
        // Selects the matching value in the drop-down
        EnsureItems();
        ddMtg.SelectedValue = System.Convert.ToString(value);
    }
}


/// <summary>
/// Returns an array of values of any other fields returned by the control.
/// </summary>
/// <returns>It returns an array where the first dimension is the attribute name and the second is its value.</returns>
public override object[,] GetOtherValues()
{
    object[,] array = new object[1, 2];
    //array[0, 0] = "mtgCode";
    //array[0, 1] = ddMtg.SelectedItem.Value;
    array[0, 0] = "listTktFunctions";

    List<string> listFunctions = new List<string>();

    foreach (ListItem thisItem in cblFunctions.Items)
    {
        if (thisItem.Selected)
        {
            listFunctions.Add(thisItem.Value);
        }
    }

    array[0, 1] = string.Join("|", listFunctions);

    return array;
}

/// <summary>
/// Returns true if a meeting is selected. Otherwise, it returns false and displays an error message.
/// </summary>
public override bool IsValid()
{
    if ((string)Value != "")
    {
        return true;
    }
    else
    {
        // Sets the form control validation error message
        this.ValidationError = "Please select the iMIS meeting code.";
        return false;
    }
}


/// <summary>
/// Sets up the internal DropDownList control.
/// </summary>
protected void EnsureItems()
{
    // Generates the options in the drop-down list
    if (ddMtg.Items.Count == 0)
    {
        DataSet data = new DataSet();

        string qs = @"
        SELECT MEETING, TITLE
        FROM [APSA_Test].[dbo].[Meet_Master]
        ORDER BY MEETING";

        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            SqlDataAdapter adapter = new SqlDataAdapter(qs, connection);
            adapter.Fill(data);
        }

        if (data.Tables[0].Rows.Count > 0)
        {
            foreach (DataRow row in data.Tables[0].Rows)
            {
                ddMtg.Items.Add(new ListItem(row["MEETING"].ToString() + " - " + row["TITLE"].ToString(), row["MEETING"].ToString()));
            }                
        }
    }
}


protected void populateFunctions(string mtgCode)
{
    DataSet data = new DataSet();

    string qs = @"
    SELECT PRODUCT_CODE, PRODUCT_CODE
    FROM [APSA_Test].[dbo].[Product_Function] pf
    WHERE PRODUCT_CODE LIKE @mtgCode + '/%'
    ORDER BY pf.PRODUCT_CODE";

    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        SqlDataAdapter adapter = new SqlDataAdapter(qs, connection);

        adapter.SelectCommand.Parameters.Add("@mtgCode", SqlDbType.NVarChar, 10);
        adapter.SelectCommand.Parameters["@mtgCode"].Value = mtgCode;

        adapter.Fill(data);
    }

    if (data.Tables[0].Rows.Count > 0)
    {
        foreach (DataRow row in data.Tables[0].Rows)
        {
            cblFunctions.Items.Add(new ListItem(row["PRODUCT_CODE"].ToString(), row["PRODUCT_CODE"].ToString()));
        }
    }
}


protected void ddMtg_SelectedIndexChanged(object sender, System.EventArgs e)
{
    cblFunctions.Items.Clear();
    populateFunctions(ddMtg.SelectedValue);
}


/// <summary>
/// Handler for the Load event of the control.
/// </summary>
protected void Page_Load(object sender, EventArgs e)
{
    // Ensure drop-down list options
    EnsureItems();
}

Any insight is much appreciated.

Thanks, Pam