y.x = 4

z = y

Public Class Form1
    Dim y As New clsA
    Dim z As New clsA
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        AddHandler y.NewValue, AddressOf PopupMessage
        AddHandler z.NewValue, AddressOf PopupMessage
        y.x = 4
        z = y
    End Sub
 
    Private Sub PopupMessage()
        MessageBox.Show("neuer Wert")
    End Sub
End Class
 
 
Class clsA
    Dim pX As Integer
 
    Property x() As Integer
        Get
            Return pX
        End Get
        Set(ByVal value As Integer)
            pX = value
            RaiseEvent NewValue()
        End Set
    End Property
 
    Event NewValue()
End Class