MouseEnterLeave using GetCursorPos API

Public Class Form1

    Public Declare Auto Function GetCursorPos Lib "User32.dll" (ByRef lpPoint As Point) As Integer
    Dim WithEvents TrackerRefresh As System.Timers.Timer = New System.Timers.Timer(10)
    Dim rect As Point

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        AddHandler TrackerRefresh.Elapsed, AddressOf TrackerRefresh_Elapse
        TrackerRefresh.Start()
    End Sub

    Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles MyBase.Paint
        GetCursorPos(rect)
        If (rect.X <= Me.Left Or rect.X >= (Me.Left + Me.Width)) Or (rect.Y <= Me.Top Or rect.Y >= (Me.Top + Me.Height)) Then
            Me.Opacity = 1
        Else
            Me.Opacity = 0.5
        End If
    End Sub

    Protected Sub TrackerRefresh_Elapse(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs)
        Me.Invalidate()
    End Sub

End Class