Private strPath As String = _
   System.Environment.SpecialFolder.MyComputer.ToString
 
'Das Event 
Private Event PathChanged(sender As Object, e As EventArgs)
 
Dim button1 As New Button With 
    {.Parent = Me, .Enabled = False} 'Demo, ohne Designer
 
 
Public Property StrPathCont() As String
     Get
        Return strPath
     End Get
 
     Set(ByVal value As String)
        If IO.Directory.Exists(value) Then
           strPath = value
           RaiseEvent PathChanged(Me, EventArgs.Empty)
        Else
                Throw New ArgumentException(value & " existiert nicht")
        End If
     End Set
End Property
 
 
Private Sub Path_Changed(sender As Object, e As EventArgs) Handles _
  Me.PathChanged
    button1.Enabled = True
End Sub