document.querySelector(".ObligatoryField input").addEventListener('change', function (){
                 alert('qweqwe');
                        var checkBox = document.getElementsByName('sbc2')[0];
                        if (checkBox.checked == true) {
                         //  alert('qweqwe');
                             if  ((document.querySelector(".ObligatoryField input").value.length) !== 0) {
                               document.getElementById('cb1').disabled = false; }
                             else
                             {document.getElementById('cb1').disabled = false;}
                        }
                        else {
                         document.getElementById('cb1').disabled = false;
                        }
                    });