datebox validate

[jaimi]

I'd like to check the content of a datebox at keyup-level.
So far I came to this (but it's not wrking):

 $.extend($.fn.validatebox.defaults.rules, {
   md: {
    validator: function(value, param){
    var d2 = $.fn.datebox.defaults.parser(value);
    return d2 == d2.match(/\d+/);
  },
   message: 'Geben Sie ein gültiges Format (TT.MM.JJJJ) ein.'
  }
 });

 $('#HOM_GEBURTSDATUM').datebox({
  validType: 'md'
 });
 var tb = $('#HOM_GEBURTSDATUM').datebox('textbox');
 tb.add(tb.parent())
   .css("background-color","#1a1a1a")
   .css("color","#fff");
 tb.parent().tooltip({
     position: 'right',
     content: '<span>Geben Sie das Geburtsdatum des Pferdes ein.</span>'
 }); 

Any suggestions?
thx, jaimi