Via Javascript only, check a checkboxlist to see if each item is selected, and set focus to the checkboxlist

I have a checkboxlist named "cblNSGONF". I tried using this looping to set focus that these two items under checkboxlist are checked:

• If not, an error would occur and set focus on the checkbox list.
• If all are checked, set focus on the next checkboxlist named "cblNSGONF" with just one item.

Why does this not work. See code in javascript:

   var checkboxlist1 = document.getElementsByName("cblNSGONF");
   var ischecked5 = false;
   for (var i = 0, len = checkboxlist1.Items.Count-1; i < len; i++) {
           if (checkboxlist1.item[i].selected = false) {
                    alert('Please check both checkboxes for NSGO NF Only Certification Only');
                    document.getElementById('cblNSGONF').disabled = false
                    document.getElementById('cbCertify').removeAttribute("checked");
                    document.getElementById('btnSubmit').disabled = true;
                    document.form1.cblNSGONF_0.focus();
                    document.getElementById('lblNSGONFCheckboxes').style.display = "inherit";
                    return;
                    ischecked5 = true;
                    //var cblNSGONFValue = checkboxlist1[i].value;
                    break;
                }
            }

            alert('This is ischecked5 value: ' + ischecked5+ '');

            if (ischecked5 = false) {
                alert('Please check both checkboxes for NSGO NF Only Certification Only');
                document.getElementById('cblNSGONF').disabled = false
                document.getElementById('cbCertify').removeAttribute("checked");
                document.getElementById('btnSubmit').disabled = true;
                document.form1.cblNSGONF_0.focus();
                document.getElementById('lblNSGONFCheckboxes').style.display = "inherit";                                    
                return;
            }

The alert is always getting evaluated to ischecked5 equal false. Why?