private void Entry_TextChanged(object sender, TextChangedEventArgs e)
{
vm.NewTender.TenderAmount = vm.NewTender.TrnCollectionLines.Sum(x => x.Amount);
vm.NewTender.ChangeAmount = vm.NewTender.TrnCollectionLines.Sum(x => x.Amount) - vm.SelectedSale.TrnSalesLines.Sum(x => x.Amount);
vm.RefreshTender();
}