qualcosa del genere?
codice:
<html>
<head>
<script language="javascript">

function conferma(m,f) {
  if (confirm(m,m)) {
    f.submit();
  }
}
</script>
<body>
<form name="myform" action="http://www.google.com">
<input type="radio" name="myradio" value="1" onClick="conferma('Sei sicuro?', this.form);">
</form>
</body>
</html>