codice:
    Sub AbilitaDisabilitaTextBox(ByVal ctr As Control, ByVal enabled As Boolean)
        For Each ctr In ctr.Controls
            If TypeOf ctr Is TextBox Then
                DirectCast(ctr, TextBox).Enabled = enabled
            End If
            AbilitaDisabilitaTextBox(ctr, enabled)
        Next
    End Sub
si richiama con:

codice:
AbilitaDisabilitaTextBox(Me, False)