How to cut & redo text on mdi form to child form

hi
I am using An mdi form which contain many child form and mdi form contain ToolStrip1 in that redo & cut button are not working please help me out of this

Private Sub toolredo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles toolredo.Click

    Dim activeChild As Form = Me.ActiveMdiChild
    If (Not activeChild Is Nothing) Then
    Try
    Dim tb As TextBox = CType(activeChild.ActiveControl, TextBox)
    If TextBox.CanRedo = True Then
    If TextBox.redo Then
    TextBox.Redo()
    End If
    End If
    Catch
    MessageBox.Show("You need to select a TextBox.")
    End Try
    End If
    End Sub