On top of Adam's great scripts - I would also add in the following if your calendar could be one that the user will add to with their own stuff - Add in a "tag" to the event, so that when you are running through and deleting the previously automatically created events - check for the key and remove only those events.
newEvent.setTag(myKey, 'myValue-Doesn't matter what as we only check for existence of tag, not its content');
There's a bit on filtering by using the tag
here - but as
Tanaike points out in the comments, it uses a lot of process to do it. In my code to do this, I just grab all the events between today's date (don't care about past ones) and a specified date in the future, and check for the tag before deleting only those ones.
if (allEvents[e].getTag(myKey)!==null){
Hope this helps.
Laurie