Dynamicly change SWF on Loaded page

Hello I’m traying to update a SWF on a page tha has been fully loaded via javascript. The catch is that the SWF is in the hard drive of a local machine. and I’m calling a javascript function on the onchange event of a file field.

Here is my code:

forms.uploadFlash.uploadFlashfield.onchange =function(){
var objCont = document.getElementbyId(‘container’);
var docObj = document.createElement(‘embed’);
docObj.src= this.value;

the code works fine with a server side SWF but it doesn’t work with a local file.