private void btnSave_Click(object sender, EventArgs e)
        {
            SetEntryExpenses();
            if (isEditMode && OldModel.Value != Model.Value)
            {
                OldModel.Value *= -1;
                controller.PerformTransaction(OldModel);
                controller.Remove(OldModel);
            }

            if (Model.PaymentMethod is Account)
            {
                controller.PerformTransaction(Model);
            }
            else if (!isEditMode)
            {
                if (ckRepeat.Enabled && ckRepeat.Checked)
                {
                    Model.CaptionRepeat = $"(1/{nupTimes.Value})";
                    controller.SplitAccount(Convert.ToInt32(nupTimes.Value), Model.Clone());
                }
                else
                {
                    controller.PerformTransaction(Model);
                }
            }

            controller.Save(Model);
            DialogResult = DialogResult.OK;
            this.Close();
        }