Bootstrap-datepicker set multidate attributes on fly

Question

I need to update 'multidate' attribute on changing a no of days drop down.

What i have done :

Datepicker initialize

$('.datePickerBenner').datepicker({ 
        multidate: 7,      
        format: 'yyyy-mm-dd', 
        startDate: new Date(),
        datesDisabled: unavailableDates,
        autoclose: false,
        numSelectable : 2,
    });

Changing multidate on dropdown

$(".no_of_days").change(function() {
    var max_no_of_days = $(this).val();  
    $('.datePickerBenner').datepicker("multidate", max_no_of_days);  
});

It should restrict no. of dates as per selected drop down but its not working.