急大家给看看代码是什么意思？解决办法

急，大家给看看代码是什么意思？
Private Sub MDIForm_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
 On Error Resume Next
  Image1(PrevButton).BorderStyle = 0
  Image2(PrevButton).Visible = True
  PrevButton = -1
End Sub

------解决方案--------------------
是这样的:
PrevButton = -1时
Image1(PrevButton).BorderStyle = 0
Image2(PrevButton).Visible = True
都要报错,由于用了
On Error Resume Next
那么
Image1(PrevButton).BorderStyle = 0
Image2(PrevButton).Visible = True
就不会被反复执行了.