Form submit e result() call sequence in autocomplete

Form submit e result() call sequence in autocomplete

I have an input field that with autocomplete with mustMatch option because i want that what is input is exactly in the list.
Input field is valued from result call-back function:
                }).result(function(event, item, formatted) {
                        if(item){
                            $(this).attr('name', item['@type']);
                            if($(this).val()!=formatted) {
                                $(this).val(formatted);
                            }
                        }
                }).blur(function(){
                    $(this).search();
                });

this code take care that if i input "roma"  the autocomplete don't take "Emilia Romagna" that is the first option.
I cannot use exact match because are name of location and same times you know only partial name like Milanese that gave as suggestion "San Donato Milanese" or "Settimo Milanese".

This it works if i use tab or mouse or any kind of key except ENTER... because when i press ENTER submit is called before result() func.
Take care that i would like to not change the actual submit function because is shared between jquery e NON jquery FORM