I would like to update the flashvars value argument to view another video:
I foun
If you want to change the flash vars and reload the Flash, you should just remove the SWF from the DOM and embed it again with your new vars (using SWFObject or whatever other method suits your fancy!).
If you want to change the flash vars without reloading the Flash, you're out of luck: there's no officially-supported way. In this case, you should use ExternalInterface to call ActionScript methods that update your values from JavaScript.