Lag Generator

ok i got a preloader but i want it to run smoothly i added a line to generate lag but i am not familiarized yet with the operators and the lag for the loading bar is not working, what is wrong?

bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
**percent -= (percent-((bytes_loaded/bytes_total)*100))*.25;**
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+"%";
if (bytes_loaded == bytes_total) {