Private Nummer As Integer
 
    Public Event changed()
 
    Public Property var() As Integer
        Get
            Return Nummer
        End Get
        Set(ByVal value As Integer)
            Nummer = value
            RaiseEvent changed()
        End Set
    End Property
 
    Private Sub Class1_changed() Handles Me.changed
        TextBox1.Text = Nummer
    End Sub

Private Sub U_Form_anzeigen
      Dim a As new Class1.Klasse
      a.MdiParent = Me
      a.Show()
      a.WindowState = FormWindowState.Maximized
End Sub
 
Private Sub DatenSenden(ByVal Nummer As Integer)
       Dim a As New Class1.Klasse
 
       For Each MdiClient In Me.MdiChildren
       If MdiClient Is a Then
           a.var = Nummer
       End If
    Next
End Sub