PageSizeComboBox" as follows:

 Protected Sub grid_ItemCreated(ByVal sender As Object, ByVal e As Telerik.Web.UI.GridItemEventArgs) Handles grid.ItemCreated

        If TypeOf (e.Item) Is GridPagerItem Then
            Dim pageBoundItem As GridPagerItem = DirectCast(e.Item, GridPagerItem)
            Dim PageSizeComboBox As RadComboBox = TryCast(pageBoundItem.FindControl("PageSizeComboBox"), RadComboBox)

            If PageSizeComboBox IsNot Nothing Then

        'Start **Page Size initialization
        Dim itemIndex As Integer = 0
        Dim minPageSize As Integer
        Dim maxPageSize As Integer
        Dim pageSizeStep As Integer
        Integer.TryParse(ConfigurationManager.AppSettings("MinPageSize").ToString(), minPageSize)
        Integer.TryParse(ConfigurationManager.AppSettings("MaxPageSize").ToString(), maxPageSize)
        Integer.TryParse(ConfigurationManager.AppSettings("PageSizeStep").ToString(), pageSizeStep)
        'End **Page Size initialization

        Dim ComboItem As RadComboBoxItem
        For iCount As Integer = minPageSize To maxPageSize Step pageSizeStep
            Dim newComboItem As RadComboBoxItem = PageSizeComboBox.Items.FindItemByValue(iCount)
            If newComboItem Is Nothing Then
                ComboItem = New RadComboBoxItem(iCount.ToString(), iCount.ToString())
                ComboItem.Attributes.Add("ownerTableViewId", gridClientId)
                PageSizeComboBox.Items.Insert(itemIndex, ComboItem)
            End If
            itemIndex += 1
        Next

        Dim newItem As RadComboBoxItem = PageSizeComboBox.Items.FindItemByValue(gridDataItemCount.ToString())
        If newItem Is Nothing Then
            ComboItem = New RadComboBoxItem("All", gridDataItemCount.ToString())
            ComboItem.Attributes.Add("ownerTableViewId", gridClientId)
            PageSizeComboBox.Items.Insert(PageSizeComboBox.Items.Count, ComboItem)
        Else
            newItem.Text = "All"
        End If

                AddHandler PageSizeComboBox.SelectedIndexChanged, AddressOf Me.PageSizeComboBox_SelectedIndexChanged
                PageSizeComboBox.AutoPostBack = True
            End If
          
        End If

    End Sub

Public Sub PageSizeComboBox_SelectedIndexChanged(ByVal sender As Object, ByVal e As RadComboBoxSelectedIndexChangedEventArgs)

        Dim intPageSize As Integer

        Integer.TryParse(e.Value, intPageSize)
        ViewState("intPageSize") = intPageSize.ToString()

        grid.PageSize = ViewState("intPageSize")
        grid.Rebind()

    End Sub