Flashvars and Javascript

So I am trying to pass anything from javascript to an object, and use flashvars to retrieve its definition. Is it even possible? Here is the code-

Javascript

var user = window.external.GetUsername;	
	
page_request.open('GET', 'http://www.mysite/members/tb/get_avatar.php?username='+user, true);
page_request.send(null);
</script>

Flashvars just beneath it

<object width="200" height="200" type="application/x-shockwave-flash" data="flashvars_as3.swf">
<param name="flashvars" value="myUser=user&delay=myDelayDefinition&loop=myLoopDefinition"/>
</object>

Of course this doesn’t work. I am wondering though, how would I get that variable “user” that is created in the javascript code, back to flash?

Ty in advance (-: