Public Class Form1
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dialog1.Tag = "Hallo"
        If Dialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
            MsgBox(Dialog1.Tag)
        Else
            MsgBox("NICHTS")
        End If
    End Sub
End Class

Public Class Dialog1
 
    Private Sub OK_Button_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles OK_Button.Click
        Me.Tag = "Hallo zurück!"
        Me.DialogResult = System.Windows.Forms.DialogResult.OK
        Me.Close()
    End Sub
 
    Private Sub Cancel_Button_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Cancel_Button.Click
        Me.DialogResult = System.Windows.Forms.DialogResult.Cancel
        Me.Close()
    End Sub
 
    Private Sub Dialog1_Load(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Me.Load
        Me.Text = Me.Tag
    End Sub
 
End Class