The info is stored in the Calendar Profile
Here is code you can email in a button to the user that will remove the profile
Dim session As New NotesSession
Dim db As NotesDatabase
Dim doc As NotesDocument
Set db=session.CurrentDatabase
Set doc=db.GetProfileDocument("CalendarProfile")
Call doc.remove(True)
If doc Is Nothing Then
MsgBox "Profile Document Was Successfully Removed"
Else
MsgBox "Profile Document WAS NOT Removed",48
End if