you could do something like wait til the movie is loaded and send a message from javascript to the movie nd if it gets there then you know you're working, do the pop-up, therwise just link to a new page...maybe:
ActionScript Code:
//in the web page
function sayHello() {
document.movie.SetVariable("saidHello","true");
}
//in the movie
saidHello = false;
getURL("javascript:sayHello();");
if(!saidHello) {
//do one thing
} else {
//do the other
}
providing your movie has the name and id parts of the html tags set to 'movie'
learning from experience, I tried this code and it works