Thanks for the post. The easiest way is to delete the appointments is via the diary grid view. To do this please follow the steps below:
1) Click on the Switch to Grid View blue link (Next to the Diary Options button)
2) Click on the Search button
3) Search on Staff and select the staff member in question
4) If you know of a date range you can enter this into the Start field
5) Click OK when you are happy with this
When you can see the appointments in question group select them and delete them.