Private Sub clearImages(ByVal ctrl As Control)
        Dim btn As Button
        For Each sub_ctrl As Control In ctrl.Controls
            clearImages(sub_ctrl)
        Next
        If TypeOf ctrl Is Button Then
            btn = CType(ctrl, Button)
            If Not btn.BackgroundImage Is Nothing Then
                btn.BackgroundImage.Dispose()
                btn.BackgroundImage = Nothing
            End If
            btn.Dispose()
            btn = Nothing
        Else
            ctrl.Dispose()
            ctrl = Nothing
        End If
    End Sub