google has an application for the BB called "Google Sync".. install that to your BB and you'll be able to directly sync your BB calendar to your Google calendar and vice versa.
It works great!!
Also, it will only sync appointments made after the app is installed. You can just delete and reenter them though and it will work fine.
It does exactly what it says it will do. But, it will sync EVERYTHING in your BB, paying absolutely no attention to what calendar it was created with, to your google calendar. I use 2 calendars on my BB - one personal and one work. Google Sync just lumps them all together into Google Calendar.