用ListImage做图片的上一张和下一张的切换 ！求高手帮助~谢谢了，紧急呀

用ListImage做图片的上一张（+）和下一张（-）的切换。有四张图片，有控件Button1作为上一张（+）和Button2作为下一张（-） 。并且在Label2中告知用户，这是第几张图片（必须与图片顺序号码相符），当点击上一张为最后一张图片时，能切换到第一张图片并能继续重复阅览，点击下一张时也能灵活切换~
Public Class Form1
    Dim i As Integer
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Label1.ImageIndex = i
        i = i + 1
        Label2.Text = "当前显示的是第" & i & "张图片"
        Label2.Left = (Me.Width - Label2.Width) / 2
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        i = i + 1
        If i = 5 Then
            i = 1
        End If

        Label1.ImageIndex = Label1.ImageIndex + 1
        Label2.Text = "当前显示的是第" & i.ToString & "张图片"

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        i = i - 1
        If i = 1 Then
            i = 5
      
        End If
        Label1.ImageIndex = Label1.ImageIndex - 1
        Label2.Text = "当前显示的是第" & i & "张图片"
    End Sub
End Class
这个是我的代码，求助高手帮忙~~谢谢了