[flexcoders] How to wite a javascript that calls to ActionScript

[wkolcz]

Can someone show me how to write a javascript function that calls to a Flex/AS 
function before a browser window closes?

In my AS contructor I have:
if (ExternalInterface.available)
        ExternalInterface.addCallback("tagWithClosed",windowClosed);

I tried something like this, but I don't know how to actually invoke the 
correct function name. The swf is FXVideo.swf, the swf id is FXVideo and the 
.as file is FXVideo.as:
<SCRIPT LANGUAGE="JavaScript">
window.onbeforeunload = closingWindow;
function closingWindow()
{
   FXVideo.tagWithClosed();
}
</SCRIPT>

I would greatly appreciate it if someone could help me write this. Project due 
tomorrow.