asp.net loop dynamic checkboxlists' items - demo code included - cant access dynamic checkboxlistitems

seems its not easily possible to get access to the values of dynamically created controls in asp.net.
i read a bucketload of articles, but can't get anything to work
i setup a quick example with the idea of somebody perhaps seeing where im going wrong

in the code, there are 3 items in a radioboxlist
when the selectedindexchanged event is fired for the radioboxlist, then a checkboxlist is filled, and the contents is dependant on the value of the selected radioboxlist item.
e.g. you select "CARS" (radioboxlist item)
and the checkboxlist item will fill with selected cars.
the checkboxlist is a dynamic control and there can be more than one checkboxlists e.g. ferraris in one checkboxlist, porches in another checkbox list.

the crux is that i need to save which dynamically created checkboxlist items have been checked, when the selectedIndexChanged event  is fired, (and when the user then gets back to CARS, the easy part then is to re-check the items).
(access dynamically created controls)

however i cannot access the dynamically created items, at least now during the radiobuttonlist. selectindexchanged event

could someone please help me to get a list of selected checkboxlist items?


attached is a simple aspx and .vb page with all the code to show the example
 

Partial Class Default2
    Inherits System.Web.UI.Page
    Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not Page.IsPostBack Then
            'add 3 arbitrary values to radiobuttonlist
            rbl.Items.Add("Cars")
            rbl.Items.Add("Trucks")
            rbl.Items.Add("Trailers")
        End If


    End Sub

    Protected Sub rbl_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles rbl.SelectedIndexChanged
        SaveCheckBoxes()

        'create new checkboxes here for selected value
        CreateNewCheckBoxListItems()

    End Sub
    ''' <summary>
    ''' Loop through all the dynamically created checkboxlists and save the values to HiddenField1
    ''' </summary>
    ''' <remarks></remarks>
    Protected Sub SaveCheckBoxes()

        For Each FormCtrl As Control In Form.Controls
            For Each ContentControl As Control In FormCtrl.Controls
                If TypeOf ContentControl Is Panel Then
                    For Each ChildControl As Control In ContentControl.Controls
                        If TypeOf ChildControl Is CheckBoxList Then
                            For Each MyCheckBox As ListItem In CType(ChildControl, CheckBoxList).Items
                                If MyCheckBox.Selected = True Then
                                    HiddenField1.Value = HiddenField1.Value & "," & MyCheckBox.Text
                                End If
                            Next MyCheckBox
                        End If
                    Next
                End If
            Next
        Next
    End Sub
    Protected Sub CreateNewCheckBoxListItems()
        Dim iLoop As Integer = 0
        Select Case rbl.SelectedItem.Text

            Case "Cars"

                Dim NewCheckBoxList As New CheckBoxList
                NewCheckBoxList.ID = "CheckBoxListCars1"
                NewCheckBoxList.Items.Add("TestCars1")
                NewCheckBoxList.Items.Add("TestCars2")
                NewCheckBoxList.Items.Add("TestCars3")
                panel1.Controls.Add(NewCheckBoxList)

            Case "Trucks"
                For iLoop = 0 To 3
                    Dim NewCheckBoxList As New CheckBoxList
                    NewCheckBoxList.ID = "CheckBoxListTrucks" & iLoop
                    NewCheckBoxList.Style("Position") = "Absolute"
                    NewCheckBoxList.Style("Top") = "100px"
                    NewCheckBoxList.Style("left") = iLoop * 200 + 200 & "px"
                    NewCheckBoxList.Items.Add("TestTrucks" & iLoop & "A")
                    NewCheckBoxList.Items.Add("TestTrucks" & iLoop & "B")
                    NewCheckBoxList.Items.Add("TestTrucks" & iLoop & "C")
                    NewCheckBoxList.Items.Add("TestTrucks" & iLoop & "D")
                    panel1.Controls.Add(NewCheckBoxList)
                Next

                
            Case "Trailers"
                For iLoop = 0 To 3
                    Dim NewCheckBoxList As New CheckBoxList
                    NewCheckBoxList.ID = "CheckBoxListTrailers" & iLoop
                    NewCheckBoxList.Items.Add("TestTrailers" & iLoop)
                    panel1.Controls.Add(NewCheckBoxList)
                Next

        End Select
    End Sub
  
End Class





------------------------------------
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default2.aspx.vb" Inherits="Default2" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>

  <form runat="server" id="mainForm" method="post">
      &nbsp;<div class="exampleWrapper">
          &nbsp;
        &nbsp;&nbsp;</div>
      <table>
          <tr>
              <td style="width: 725px; height: 16px">
                  <asp:RadioButtonList ID="rbl" runat="server" AutoPostBack="True" BorderStyle="Ridge" RepeatDirection="Horizontal">
                  </asp:RadioButtonList></td>
          </tr>
      </table>
      <asp:Panel ID="panel1" runat="server" Visible="true" Height="85px" Width="728px">
                  &nbsp;&nbsp;&nbsp;
    </asp:Panel>
      &nbsp;&nbsp;
      <asp:HiddenField ID="HiddenField1" runat="server" />
  
 
      
    </form>

</body>
</html>

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