Firefox Add-on Needed To Measure Site Bandwidth

I've been looking all over for an app (preferably a firefox add-on) which shows in real time the current bandwidth consumption of a site.Basically I'm wanting to measure the amount of data being transmitted from the site while I have an AJAX script running and i'm having trouble locating anything like that. It's just so I can predict overall bandwidth consumption for X amount of users at any given time and adjust the refresh rate to compensate (currently refreshing 10 rows of MySQL data every 1,000 microseconds during testing).There are tonnes of add-ons for firefox that measure your current bandwidth speed and so on but that's not what i'm looking for so please don't post anything like that. Just an add-on that shows current consumption, not speed.Thanks guys, night all.

I think that cannot be done thorough a Firefox add-on because it’s something related to the web server. But there are add-ons that will let you know the data transfer between the site and your PC.

Yeah when I wrote this I wasn't really thinking straight and trying to iron out about 20 different problems in my head at once. I forgot about the advanced statistics features in cPanel

I agree, this seems a sever statistics need, which can be fulfilled only by a server-side tool, and network traffic monitor available with your cpanel should be the best solution.