One field's value as a part of another field

Hi,

I customized Ecommerce.Address Module and added two new fields: AddressProvinceID and AddressCityID.

Form control for Both of them are Dropdownlist and AddressCityID depends on AddressProvinceID and Dropdownlist of AddressCityID fills with data accourding to selected AddressProvinceID.

SQL query for AddressProvinceID data source is: SELECT -1 as ProvinceID, '(Select)' as ProvinceDisplayName UNION SELECT ProvinceID, ProvinceDisplayName FROM CustomTable_Province

and SQL query for AddressCityID data source is: SELECT -1 as CityID, '(Select)' as CityDisplayName UNION SELECT CityID, CityDisplayName FROM CustomTable_City INNER JOIN CustomTable_Province ON CustomTable_City.CityProvinceID = CustomTable_Province.ProvinceID WHERE CustomTable_City.CityProvinceID = {% AddressProvinceID %}

The problem is when I set both of them in checkout process and go to the next step the value of AddressCityID not saving.

Also when I debug the macro, {% AddressProvinceID %} returns two times, -1 for first time and then returns correct value of selected AddressProvinceID.