internet (without LAN) monthly traffic statistics

[Dj YB]

hello,
does anyone know of a good (working) program for monthly internet usage stats
I need this info to stay under my monthly traffic cap.
I am using a single ethernet connection for LAN and internet.

iptraf is really complicated and require too many changes,
vnstat doesn't support the separation using single interface...
any help on this matter will be greatly appreciated.

using Fedora 11 KDE 4.3.2

I won't be able to read emails in the next two weeks so no rush :-)

thanks,
YB.