$(document).ready(function() {
    function disableFieldset(cid, fid) {
        var checkbox = $(cid);
        var initial = checkbox.is(":checked");

        var questions = $(fid)[inital ? "removeClass" : "addClass"]("gray");
        var questionInputs = questions.find("input").attr("disabled", !inital);
        var questionSelects = questions.find("select").attr("disabled", !inital);

        checkbox.click(function() {
            questions[this.checked ? "removeClass" : "addClass"]("gray");
            questionInputs.attr("disabled", !this.checked);
            questionSelects.attr("disabled", !this.checked);
        });

        return this;
    }

    disableFieldset("#checkbox1", "#fieldset1");
    disableFieldset("#checkbox2", "#fieldset2");
});