LanguageCode data type

Hello experts,

I am trying to create a Language dropdown as part of my customization on the Cusotmer BO. I need a new field where we could specify the Customer's langauge for communication. When I try to create this field I get an error.

"Error    3    Definition of data type 'LanguageCode' not found. Add an import statement for the missing namespace or use a fully qualified name."

Here is how my code looks like

import AP.Common.GDT as apCommonGDT;

import AP.FO.BusinessPartner.Global;

[Extension] businessobject AP.FO.BusinessPartner.Global:Customer raises MsgERPData, MsgERPData_FI, MsgIndividualCustomer, MsgIndividualCustomer_FI {

        // You must activate this business object before you can access the extension fields

        // or messages in script files, forms, and screens.

           node AddressInformation {

           }

        message MsgERPData text "Fill mandatory data required for promoting the Prospect to Customer";

        node Common {

        [Label ("Language")] element KNA1_LANGU:LanguageCode;

        [Label ("E-mail")] element ADR6_SMTPADDR:LANGUAGEINDEPENDENT_EXTENDED_Text;

        //[Label ("Region")] element KNA1_REGIO:LANGUAGEINDEPENDENT_EXTENDED_Text;

Should it be possible to use this datatype or should we create a custom codelist for this?