Плавное исчезновение картинки

Public Class Form1
#Region "Графика. Переменные"
    Dim proz As Single = 1.0!
    Dim OverImage, UnderImage As Image
    Dim ia As Imaging.ImageAttributes = New Imaging.ImageAttributes
    Dim cm As Imaging.ColorMatrix = New Imaging.ColorMatrix(New Single()() _
    {New Single() {1, 0, 0, 0, 0}, _
    New Single() {0, 1, 0, 0, 0}, _
    New Single() {0, 0, 1, 0, 0}, _
    New Single() {0, 0, 0, 1, 0}, _
    New Single() {0, 0, 0, 0, 1}})
#End Region
 
#Region "Кнопка Закрыть"
#Region "Таймер"
    Private Sub TimerExitIn_Tick(sender As Object, e As EventArgs) Handles TimerExitIn.Tick
        proz -= 0.05!
        If proz < 0.0! Then
            proz = 0.0!
            TimerExitIn.Enabled = False
        End If
 
        cm.Matrix33 = proz
        ia.SetColorMatrix(cm)
 
        With ButtonExit
            Dim g As Graphics = Graphics.FromImage(.Image)
            g.DrawImage(UnderImage, 0, 0)
            g.DrawImage(OverImage, _
            Rectangle.Round(OverImage.GetBounds(GraphicsUnit.Pixel)), 0, 0, _
            UnderImage.Width, UnderImage.Height, GraphicsUnit.Pixel, ia)
            g.Dispose()
        End With
 
        ButtonExit.Refresh()
    End Sub
 
    Private Sub TimerExitOut_Tick(sender As Object, e As EventArgs) Handles TimerExitOut.Tick
        proz -= 0.05!
        If proz > 0.0! Then
            proz = 0.0!
            TimerExitOut.Enabled = False
        End If
 
        cm.Matrix33 = proz
        ia.SetColorMatrix(cm)
 
        With ButtonExit
            Dim g As Graphics = Graphics.FromImage(.Image)
            g.DrawImage(OverImage, 0, 0)
            g.DrawImage(UnderImage, _
            Rectangle.Round(UnderImage.GetBounds(GraphicsUnit.Pixel)), 0, 0, _
            OverImage.Width, OverImage.Height, GraphicsUnit.Pixel, ia)
            g.Dispose()
        End With
 
        ButtonExit.Refresh()
    End Sub
#End Region
    Private Sub ButtonExit_MouseMove(sender As Object, e As MouseEventArgs) Handles ButtonExit.MouseMove
        TimerExitIn.Interval = 10
        TimerExitIn.Enabled = True
    End Sub
 
    Private Sub ButtonExit_MouseLeave(sender As Object, e As EventArgs) Handles ButtonExit.MouseLeave
        TimerExitOut.Interval = 10
        TimerExitOut.Enabled = True
    End Sub
#End Region
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        OverImage = New Bitmap(My.Resources.Закрыть_1)
        UnderImage = New Bitmap(My.Resources.Закрыть_2)
        ButtonExit.Image = OverImage.Clone
        ButtonExit.Size = New Size(OverImage.Width, OverImage.Height)
    End Sub
End Class