Zulu

Zulu is a server-side plugin for FileMaker Server that lets iCal see your FileMaker tables as iCal calendars.

You can edit your records in iCal and, when you do, you're editing the FileMaker records directly. iCal will even respect FileMaker's record locking if someone else is editing the record when you try to do the same.
There are no scripts to run when you edit records, and no need to try and keep iCal and FileMaker in sync: with Zulu, iCal is reading your FileMaker records from the server, just like FileMaker does. iCal becomes another FileMaker client.