When I create new calendar entries on my BlackBerry, they show up on my Google Calendar. However, if I modify the entry later on my phone (such as to reschedule the event) the event does not update in my Google Calendar. 

Also, when I make entries directly into my Google Calendar via the internet they do not show up on my BlackBerry. 

I have downloaded Google Sync but I am afraid to run the program, because the options for the app show that events older than 4 weeks are not kept. I do not want to lose any events either on my device or on my Google calendar, as I need these for my personal records. 

Any advice on how I can get my phone to sync with the Calendar program without losing any data? 

Thanks in advance for the help!