G'day Community!

Love Zimbra - fantastic product. I'm investigating what ways we could integrate our time billing system with Zimbra so that:
1. Users can easily view time billing entries in their Calendar (or a special Time Billing Calendar), providing a view of billable time vs non-billable
2. Assign time billing information to calendar entries, eg. select client account, job#, work order
3. Read/write the billing information to an external system

(Or any other suggestions!)

I've read this partially completed series of Wiki articles:
http://wiki.zimbra.com/index.php?title=User:JoshPrismon

It's pretty inspiring stuff, but incomplete. So I was wondering if anyone has done this before? Or can provide some directions/URL's on how this may be done or tips on how to start.

Any help greatly appreciated!