Varien.searchForm.prototype.initAutocomplete = function(url, destinationElement,options){
        new Ajax.Autocompleter(
            this.field,
            destinationElement,
            url,
            Object.extend({
                paramName: this.field.name,
                minChars: 2,
                updateElement: this._selectAutocompleteItem.bind(this)
            }, options || {})
        );
    };