iCal: syncronizing two computers

Hello everyone. I'm not sure what I'm looking for here. I use two computers; one for working at home and one for working at work. I use a small portable HDD to work on files I use/need. Is there a way to synchronize both my iCal calendars regardless of which one I enter an appointment into? In other words, how can I add to the other so they are the same regardless of which one I last used, without doing it twice obviously? Does this make sense?

The iMac is running 10.3.9. The MacBook is running 10.4.7.

 

Well, I do feel there should be a way to do it without relying on a monthly service charge. I did find a beta application called MySync; however, it requires both computers to be running 10.4 and I don't intend on upgrading my OS until, maybe, 10.5.

 

I have found a syncronous application. However, I need to locate "my" calander files of which I have six of them.

Does anyone know if my calanders happen to be under the folders MacBook>Users>Home>Library>Application Support>iCal>Sources ?

 

SilverKeeper. However, I found out the file structure is different for 10.3. Soooo, I can't do it like I hoped unless I buy 10.4 for the iMac which I'm not going to do this close to 10.5.