function insert(aTag, eTag, formName, textAreaName) {
  var input = document.forms[formName].elements[textAreaName];
  input.focus();
  if(typeof input.selectionStart != 'undefined')
  {
    /* Einfügen des Formatierungscodes */
    var start = input.selectionStart;
    var end = input.selectionEnd;
    var insText = input.value.substring(start, end);
    input.value = input.value.substr(0, start) + aTag + insText + eTag + input.value.substr(end);
    /* Anpassen der Cursorposition */
    var pos;
    if (insText.length == 0) {
      pos = start + aTag.length;
    } else {
      pos = start + aTag.length + insText.length + eTag.length;
    }
    input.selectionStart = pos;
    input.selectionEnd = pos;
  }
}