jquery progressbar update in web application

how to increment a jquery progressbar in a web application on a button click when we upload a folder .the increment should be the size of each file in the folder.how to write the function update progressbar in jquery with each file size increment  and where to cal that method.i downloaded jquery 1.3.2 and using that.all my straming of files was written in wcf and iam consuming that service at my client side.code behind lang is c#.net

Thanks in advance

Shravajj