How to handle the following exception :The control collection cannot be modified during DataBind, Init, Load, PreRender or Unload phases.

 Public Sub CreateTabl()
        Dim ScrObjects As New ScreenObjects
        Dim buLabl As New Label
        Dim tblBu As New Table
        Dim tr As TableRow
        Dim td As TableCell
        Dim tb As New Table
        'Dim txtbx As TextBox
        Dim ddlst As WebControls.DropDownList

        tb.Font.Size = 10
        tb.BorderWidth = 1
        tb.BorderStyle = BorderStyle.Solid
        tb.CellPadding = 4
        tb.CellSpacing = 0
        tb.ForeColor = Drawing.Color.Black
        tb.Width = 700
        tb.GridLines = GridLines.Both
        tb.Style.Add("align", "center")
        tb.Style.Add("text-align", "center")

        tr = New TableRow
        tr.ID = "trHdr"
        td = New TableCell
        td.Text = "Answer"
        td.ID = "tdAns"
        tr.Controls.Add(td)
        td = New TableCell
        td.Text = "Min Value"
        td.ID = "tdMinValue"
        tr.Controls.Add(td)
        td = New TableCell
        td.Text = "MaxValue"
        td.ID = "tdMaxValue"
        tr.Controls.Add(td)
        td = New TableCell
        td.Text = "Description1"
        td.ID = "tdDescription1"
        tr.Controls.Add(td)
        td = New TableCell
        td.Text = "Description2"
        td.ID = "tdDescription2"
        tr.Controls.Add(td)
        td = New TableCell
        td.Text = "Currency"
        td.ID = "tdCurrency"
        tr.Controls.Add(td)
        td = New TableCell
        td.Text = "Scale Multiplier"
        td.ID = "tdScaleMultiplier"
        tr.Controls.Add(td)
        tb.Controls.Add(tr)
For i As Integer = 1 To ddlst_Scale_Type.SelectedValue
           buLabl = New Label
           buLabl.Text = "lbl" & i
           tr = New TableRow
           tr.ID = "trData_" & i
           td = New TableCell
           td.ID = "tdData_" & i & "0"
           td.Controls.Add(buLabl)
           tr.Controls.Add(td)
           pklst = New IMaCS.Framework.UI.ImacsListControls.PickList.PickListControl
           pklst = ScrObjects.createPKLIST_grid(PickList.PickListTypes.MST_CURRENCY, "pklstProduct" & (i), 100, "", "")
           Me.Controls.Add(pklst)
           td = New TableCell
           td.ID = "tdData_" & i & "1"
           td.Controls.Add(pklst)
           tr.Controls.Add(td)
           pklst = New IMaCS.Framework.UI.ImacsListControls.PickList.PickListControl
           pklst = ScrObjects.createPKLIST_grid(PickList.PickListTypes.MST_BUSINESS_UNIT, "pklstProcess" & (i), 100, "", "")
           td = New TableCell
           td.ID = "tdData_" & i & "2"
           td.Controls.Add(pklst)
           tr.Controls.Add(td)
           pklst = New IMaCS.Framework.UI.ImacsListControls.PickList.PickListControl
           pklst = ScrObjects.createPKLIST_grid(PickList.PickListTypes.MST_RISK_EVENT, "pklstRE" & (i), 100, "", "")
           td = New TableCell
           td.ID = "tdData_" & i & "3"
           td.Controls.Add(pklst)
           tr.Controls.Add(td)
           pklst = New IMaCS.Framework.UI.ImacsListControls.PickList.PickListControl
           pklst = ScrObjects.createPKLIST_grid(PickList.PickListTypes.MST_LOCATION, "pklstSC" & (i), 100, "", "")
           td = New TableCell
           td.ID = "tdData_" & i & "4"
           td.Controls.Add(pklst)
           tr.Controls.Add(td)
           tb.Controls.Add(tr)
       Next

       tr = New TableRow
       td = New TableCell
       td.ColumnSpan = 5
       buLabl = New Label
       buLabl.Text = " "
       td.Controls.Add(buLabl)
       td.BackColor = Drawing.Color.FromName("#c0c0c0")
       tr.Controls.Add(td)
       tb.Controls.Add(tr)

    End Sub