Dim inPanel1 As Boolean
    Private Sub Panel1_MouseEnter(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Panel1.MouseEnter
        If Not inPanel1 Then
            inPanel1 = True
            Debug.WriteLine("In Panel")
        End If
    End Sub
 
    Private Sub Panel1_MouseLeave(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Panel1.MouseLeave
        If inPanel1 Then
            Dim mp As Point = Panel1.PointToClient(MousePosition)
            If Panel1.ClientRectangle.Contains(mp) Then Return
            inPanel1 = False
            Debug.WriteLine("Panel verlassen")
        End If
    End Sub

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov