[].forEach.call(document.querySelectorAll('thead.OGB th'), th => {
  var tr = th.parentNode;

  if (tr.nodeName !== "TR") {
    return;
  }

  var tds = tr.childNodes;

  if (tds.length !== 4) {
    return;
  }

  if ( tds[0].innerText.trim() === 'Type'
      && tds[1].innerText.trim() === 'Protocol'
      && tds[2].innerText.trim() === 'Port Range'
      && tds[3].innerText.trim() === 'Source') {
    console.log('gotcha!', tr);

    var commentTxt = document.createTextNode("Comment");
    var commentDiv = document.createElement("div");
    commentDiv.appendChild(commentTxt);

    var commentTh = document.createElement("th");
    commentTh.appendChild(commentDiv);

    tr.appendChild(commentTh);

    tds.forEach(td => td.style = 'width: 20%');
  }
});