Add an extra query string to Django Grappelli's autolookup fields.

autocomplete_extra_query.js

// Add this file to your admin class throught class Media.
(function($) {
    // Add the extra querystring to the autolookup field.
    function update_lookup_querystring(obj_id) {
        id = $("#" + obj_id).val();
        $("[id^=lookup_id_linea_set-]").each(function( index ) {
            var original_href = $(this).attr('href').split('&')[0];
            $(this).attr('href', original_href + '&' + obj_id + '=' + id);
        });
    }
    // Call it somewhere.
    $(document).ready(function() {
        $(".grp-add-handler").click(function() {
            update_lookup_querystring('client_id');
        });

    });
})(grp.jQuery);

models.py

class Foo(models.Model):
    ...
    @staticmethod
    def autocomplete_queryset(*args, **kwargs):
        qs = Precio.objects.all()
        if 'client_id' in kwargs:
            qs = qs.filter(client__pk=kwargs['client_id'])
        return qs

views.py

class YPAutocompleteLookup(AutocompleteLookup):
    '''
        patch grappelli's autocomplete to let us control the queryset
        by creating a autocomplete_queryset function on the model
    '''
    def get_queryset(self):
        '''
            Send the extra querystring to your autocomplete_queryset.
            Add args/kwargs to all your autocomplete_queryset methods or validate here.
        '''
        if hasattr(self.model, "autocomplete_queryset"):
            qs = self.model.autocomplete_queryset(
                id_cliente=self.request.GET.get('client_id', None))
        else:
            qs = self.model._default_manager.all()
        qs = self.get_filtered_queryset(qs)
        qs = self.get_searched_queryset(qs)
        return qs.distinct()