Measuring internet session time

I'm running XP and have a simple question. Can I tell how long a computer has been logged onto the internet in a particular session for a given day? We subscribe to Comcast cable internet.

We placed a limit on how long my son can be on the internet when he's finished his homework, but we suspect he's been going over this limit. He's alone when he gets home from school for a few hours, so we're not sure. I know there is software that can set specific times to automatically log out, but I'd like to trust him at this point. However, if there's a simple way for me to find out how long he's been online, it would help.

Thanks so much, BDWeller

It's not about trusting your child, it's about parental resposibility (ie: go all out on this)
http://www.salfeld.com/software/parentalcontrol/index.html

Thanks for your concern. However, please understand, I've installed a draconian web censoring system that allows my boy to only be on appropriate sites. And, I have the history button to determine if he's strayed in any other way. My only question is if there is way in XP to determine how long he was on the internet (without buying something).

That's it. Nothing more. No parenting advice needed here. If there's no way to do it for free, perhaps we'll purchase the software you recommended, or, more likely one made by a U.S.-based software developer.