object, param, jquery

Have you considered using jQuery SWFObject plugin?

http://jquery.thewikies.com/swfobject/

After searching for info, it seems you cannot dynamically change the param element's attributes dynamically. The simplest way will probably be to pull the element's HTML into a variable, feed that back into jQuery, and use CSS selectors on that. Then you could clear the object and replace it with the new code.

var url = (url here);
var code = $("#embedded").html();
var newcode = $("param:first", code).attr("src", url).html();
$("#embedded").html(newcode);

or something like that... ;)