Optimize date2str function

/***************************************************
Created Date: 19 Jul 2013
Created By: Jimmy Xie (Tectura)
Helpdesk Ticket#: TB001613 - Accounts Payable Positive Pay
Description of Behavior: Format extended date
Expected Input:
Expected Output:
***************************************************/
public static str dateFormatExtended2Str_DNT(Date                   _dateValue,
                                             DNT_DateFormatExtended _dateFormatExtended,
                                             int                    _separator)
{
    #define.123 (123)
    #define.132 (132)
    #define.213 (213)
    #define.231 (231)
    #define.312 (312)
    #define.321 (321)
    #define.0   (0)
    #define.2   (2)
    #define.4   (4)

    str ret;
    ;

    switch(_DateFormatExtended)
    {
        case DNT_DateFormatExtended::ddmmyy:    ret = date2str(_dateValue,#123,#2,_separator,#2,_separator,#2); break;
        case DNT_DateFormatExtended::ddmmyyyy:  ret = date2str(_dateValue,#123,#2,_separator,#2,_separator,#4); break;
        case DNT_DateFormatExtended::ddyymm:    ret = date2str(_dateValue,#132,#2,_separator,#2,_separator,#2); break;

        case DNT_DateFormatExtended::ddyyyymm:  ret = date2str(_dateValue,#132,#2,_separator,#2,_separator,#4); break;
        case DNT_DateFormatExtended::mmddyy:    ret = date2str(_dateValue,#213,#2,_separator,#2,_separator,#2); break;
        case DNT_DateFormatExtended::mmddyyyy:  ret = date2str(_dateValue,#213,#2,_separator,#2,_separator,#4); break;
        case DNT_DateFormatExtended::mmyydd:    ret = date2str(_dateValue,#231,#2,_separator,#2,_separator,#2); break;
        case DNT_DateFormatExtended::mmyyyydd:  ret = date2str(_dateValue,#231,#2,_separator,#2,_separator,#4); break;
        case DNT_DateFormatExtended::yyddmm:    ret = date2str(_dateValue,#312,#2,_separator,#2,_separator,#2); break;
        case DNT_DateFormatExtended::yyyyddmm:  ret = date2str(_dateValue,#312,#2,_separator,#2,_separator,#4); break;
        case DNT_DateFormatExtended::yymmdd:    ret = date2str(_dateValue,#321,#2,_separator,#2,_separator,#2); break;
        case DNT_DateFormatExtended::yyyymmdd:  ret = date2str(_dateValue,#321,#2,_separator,#2,_separator,#4); break;
    }

    return ret;
}