Package name uCommerce 2.6.1.0 Package version 2.1.0.0

I am using the above version of UCommerce. We have successfully implemented promocode/voucher functionality in our installation and everything works correctly in the basket and for payments etc, however, when we limit the number of vouchers to 5 for example, how do we get the number of vouchers used to decrease in the back office after a voucher has been used for a successful payment? At the moment the number of uses of a voucher is not reflected in the back office. We apply the voucher to the basket prior for checkout as follows:

UCommerce.Xslt.Library.AddVoucher(Txt_VoucherCode.Text);                                       SiteContext.Current.OrderContext.GetBasket().Save();
TransactionLibrary.ExecuteBasketPipeline();

Thanks

Kevin