Catching an error from a child iFrame in JavaScript

Question

I have a javascript code:

<script language="javascript" type="text/javascript">
try {
     document.write("<iframe id=\"frame\" src=\"http://somewebsite.com/" + "\"scrolling=\"yes\" width=\"850\" height=\"575\" frameborder=0></iframe>");
}
catch (e) {
      alert(e.Message);
                                }
</script>

The code in iFrame generate an "Access Denied" error. How can I catch it? The way I'm doing is not showing any alert when error happened.

Thank you