SugarCRM7 Add DropDown List - Populate list with ajax

gistfile1.js

// by EvilPeri
//custom/modules/<your module>/clients/base/fields/enum/enum.js

({
          extendsFrom: 'EnumField',
          _render: function(){
             if(this.name == 'your field name here'){
               if(_.isEmpty(this.items)){
                 this.setItems();
                 return;
              }
            }
            this._super('_render');
          }.
         setItems: function(){
              if(!_.isEmpty(this.items)){
                 this._render();
             }
             //add ajax to retrieve dropdown from another source
             // this is just an example
             $.ajax({
                 url: <your url here>
                 type: POST | GET | PUT | DELETE,
                 success: _.bind(function(data){
                          this.items = data;
                           //or do whatever data manipulation you want here. 
                          //just as long as the this.items is an array
                         this.render();
                 },this);
             })
         }
})