between.jquery.js

(function ($) {
    $.fn.between = function (elm0, elm1) {
        var index0 = $(this).index(elm0);
        var index1 = $(this).index(elm1);

        if (index0 <= index1)
            return this.slice(index0, index1 + 1);
        else
            return this.slice(index1, index0 + 1);
    }
})(jQuery);