Auto update iCal

Ok, here is my problem. I have two mac's and do not want to buy a .mac account. I need a way to have my mac's share ical info with eachother in a somehwat realtime manner (I want it to update itself frequently). I have a server I can use, but I need an application for it to work. Any ideas? There must be a way to have the computer upload (and download) info every few minutes.

 

Ok, I am using this site but here is my problem. iCal has a publish option and a subscribe option. You can publish original calanders and then download them but that makes two copies of the same calader. I understand what this service is for, it is so that my calader can be echoed to other computers. I want to make it echo each of my computers to eachother though. I want both of them to edit eachothe's calader. That is not possible with my current configuration. Can anyone help me?