Why not use a typeahead with a custom valuelist that has a global method. That way, whatever function you are currently using to construct the dropdown items can be used to return the custom valuelist items. Takes away all the hassle of having to create your own dropdown:
- Custom_valuelist_global_method.png (36.9 KiB) Viewed 2617 times
As the user types, the global method will be called with the currently typed value and you can return the filtered list accordingly.