Slide effect

I am trying to achieve a slide effect for a panel named "sidebar"
I used a timer but the panel does not slide into view but just appears in its new point.
Basicaly it should slide from point -230,0 into point 0,0
What is wrong here?

Private Sub SlideButt1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SlideButt1.Click
        Timer1.Start()
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

        Dim xy As Integer
        If xy < 1 Then
            Sidebar.Location = New Point(xy, 0)
            Timer1.Stop()
        Else
            xy = -230 + 1
        End If