There is an expert that can be downloaded via the PracticeWorks Expert exchange titled "Cancelled Appts in Date Range." This expert will show you all appts within the date range set that were Cancelled with the patient name and date.
Just in case, you can get this expert with the following steps
To run the report:
Note* if this is not the first time running, to get updated information on the report and choose the option for Generate New Contact Expert.