Private Sub UltraChart1_FillSceneGraph(ByVal sender As Object, ByVal e As FillSceneGraphEventArgs) Handles UltraChart1.FillSceneGraph
        ' we want to insert the control limit box before any of the axis gridlines, so let's start by getting the index of the first gridline
        Dim indexOfFirstGridline = -1
        For current As Integer = 0 To e.SceneGraph.Count - 1
            Dim currentPrimitive As Primitive = e.SceneGraph(current)
            If TypeOf currentPrimitive Is Line Then
                ' we have found an axis gridline.
                indexOfFirstGridline = current
                Exit For
            End If
        Next
        If indexOfFirstGridline = -1 Then Return ' failed

        ' get references to the axis objects
        Dim yAxis As IAdvanceAxis = CType(e.Grid("Y"), IAdvanceAxis)
        Dim xAxis As IAdvanceAxis = CType(e.Grid("X"), IAdvanceAxis)

        Dim startX As Integer = xAxis.MapMinimum
        Dim endX As Integer = xAxis.MapMaximum
        Dim startY As Integer = yAxis.Map(0.0)
        Dim endY As Integer = yAxis.Map(0.3)

        Dim controlLimitBox As New Box(New Rectangle(startX, endY, endX - startX, startY - endY))
        controlLimitBox.PE = New PaintElement(Color.Pink)
        e.SceneGraph.Insert(indexOfFirstGridline, controlLimitBox)
    End Sub