getting IFRAME content

get iFrame content

How do I read the content from an iFrame when the page loads before its visible?

In JavaScript I am trying to read the content from an iFrame after the content has been loaded into the iFrame but before the page displays.

I am using the following function to retrieve the content.

<script language="JavaScript" type="text/javascript">

Function getIframeContent()
{
content = frames[iFView].document.body.innerHTML;

alert(content);
};

 </script>

where iFView is the frame name. I call this function at the very end of the HTML page, long after the code for loading the iFrame is run.
When the page loads the alert box comes up empty. Once the page is visible and if I call this same function again from an onclick=getIframeContent() in a button element, I get the iFrame content displayed in the alert box just fine.

What do I need to do to get it to work while the page isnt visible?