Getting the value from controls created at runtime

Hello,
I am creating  the form controls at runtime in my ASPX page on a button click event in a table designed at design time. The ID of Table is (tbl) . To this table I am adding the rows, cells and the controls called dropdownlist and a textbox in a cell at runtime.
When the user fills the values click for save button, I want to get the values from the dropdownlist saves into my database.

The code I wrote is as follows:
Private Sub btnADD_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnADD.Click
        Dim i As Short
        Dim row As TableRow
        Dim cell As TableCell
        Dim ddl As DropDownList
        Dim lst As ListBox

For i = 1 To TxtValue.Text
            row = New TableRow
            ' ADD FUNCTIONS
            ddl = New DropDownList
            ddl.ID = "function" & i
            ddl.DataTextField = "FLD_FUNCTION_DISPLAY_NAME"
            ddl.DataValueField = "FLD_FUNCTION_NAME"
            ddl.DataSource = objDS
            ddl.DataBind()

            cell = New TableCell
            cell.Controls.Add(ddl)
            row.Cells.Add(cell)

            ' ADD FIELD TEXT
            cell = New TableCell
            cell.Text = "FIELD" & i
            row.Cells.Add(cell)

            ' ADD RETURN TYPE
            cell = New TableCell
            lst = New ListBox
            lst.SelectionMode = ListSelectionMode.Single
            lst.Rows = 1
            lst.ID = "return" & i
            Dim lstItem As ListItem
            lstItem = New ListItem
            lstItem.Value = "1"
            lstItem.Text = "TRUE"
            lst.Items.Add(lstItem)
            lstItem = New ListItem
            lstItem.Value = "0"
            lstItem.Text = "FALSE"
            lst.Items.Add(lstItem)
            cell.Controls.Add(lst)
            row.Cells.Add(cell)

            ' ADD and / or
            cell = New TableCell
            If Not i = TxtValue.Text Then
                lst = New ListBox
                lst.SelectionMode = ListSelectionMode.Single
                lst.Rows = 1
                lst.ID = "andor" & i
                lst.Items.Add("AND")
                lst.Items.Add("OR")
                cell.Controls.Add(lst)
            End If
            row.Cells.Add(cell)

            tbl.Rows.Add(row)
        Next
End sub

Now I am retreiving the values inside a dropdownlist as follows:

Private Sub btnSAVE_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSAVE.Click

Dim lstBox As ListBox
For
For i = 1 To txtNumberOfRows.Text

lstBox = Page.FindControl("Form1").FindControl("tbl").FindControl("row" & i).FindControl("cell" & i).FindControl("lstreturn" & i)

Next
End sub

But I am getting the value of lstBox as nothing.

Will anyone give me the solution for this?

Looking for a kindly help.

Thank you

Nilesh