Its seems you can´t actually check when its fully loaded. But if you want to do something after it´s loaded you can use a function in javascript with setInternval and just pass the attribute until the movie gets it
function setAttribute(){
var attributes = {
id: "movie",
name: "movie"
};
swfobject.embedSWF("movie.swf", "movie", "1025", "678", "9.0.0", attributes);
var i = 1;
var sInt = setInterval(function() {
if(i >= 10) {
clearInterval(sInt);
}else{
i++;
}
//here goes the parameter you want to pass to the movie
}, 500); //increase the interval if you need it
}