How to make location field non mandatory in EP2012 expense line

Hi,

  I have modified the Location field mandatory to false.

private void SetPropertiesOnBoundFields()
    {
        ApplicationProxy.TrvExpType expenseType = this.ExpenseType;
        bool insertMode = (this.AxFormOverview.Mode == DetailsViewMode.Insert);

        foreach (DataControlField dcf in this.Group_Transaction.DataControlFieldCollection)
        {
            AxBoundField boundField = dcf as AxBoundField;
            if (boundField != null)
            {
                switch (boundField.DataField)
                {
                    case "ExchangeCode":
                        boundField.AutoPostBack = true;
                        boundField.FastTabSummary = FastTabSummary.Yes;
                        break;

                    case "CreditCardTransactionCurrency":
                        if (this.IsCreditCardTransanctionInLocalCurrency)
                        {
                            boundField.AutoPostBack = true;
                            boundField.FastTabSummary = FastTabSummary.Yes;
                        }
                        break;

                    case "DeduktionBreakfest":
                    case "DeduktionLunch":
                    case "DeduktionDinner":
                    case "Location":
                        boundField.AutoPostBack = true;                        
                        boundField.Mandatory = false;           
                        break;

its reflecting in new expense Line Form with out non mandatory but when i click save it showing field location must be filled in.

Location field not mandatory in trvexptrans table and Dataset .suggest how to make location field  non mandatory.

Thanks

Dhanasekar