function insert() {
  if (( navigator.userAgent.indexOf("Opera" ) != -1) || ( navigator.userAgent.indexOf("Netscape" ) != -1)) {
    text_before = document.eintragformular.msg.value;
    text_after = "";
  }
  else {
    document.eintragformular.msg.focus();
    var sel = document.selection.createRange();
    sel.collapse();
    var sel_before = sel.duplicate();
    var sel_after = sel.duplicate();
    sel.moveToElementText(document.eintragformular.msg);
    sel_before.setEndPoint("StartToStart",sel);
    sel_after.setEndPoint("EndToEnd",sel);
    text_before = sel_before.text;
    text_after = sel_after.text;
  }
}

function setgbcode(code) {
  insert();
  document.eintragformular.msg.value = text_before + code + text_after;
  document.eintragformular.msg.focus();
}