function insert(form,field,what)
 {
  if (document.forms[form].elements[field].createTextRange)
   {
    document.forms[form].elements[field].focus();
    document.selection.createRange().duplicate().text = what;
   }
  else if ((typeof document.forms[form].elements[field].selectionStart) != 'undefined') // für Mozilla
   {
    var tarea = document.forms[form].elements[field];
    var selEnd = tarea.selectionEnd;
    var txtLen = tarea.value.length;
    var txtbefore = tarea.value.substring(0,selEnd);
    var txtafter =  tarea.value.substring(selEnd, txtLen);
    var oldScrollTop = tarea.scrollTop;
    tarea.value = txtbefore + what + txtafter;
    tarea.selectionStart = txtbefore.length + what.length;
    tarea.selectionEnd = txtbefore.length + what.length;
    tarea.scrollTop = oldScrollTop;
    tarea.focus();
   }
  else
   {
    document.forms[form].elements[field].value += what;
    document.forms[form].elements[field].focus();
   }
 }