Use automator to change calendar alarms

I have a collection of same named calendar items that reside in a calendar that is stored in iCloud.

I would like to change the alarm settings for all these items (delete the/any current alarm and add 2 new ones e.g. one for the day before at 20:00 hours and one on the day itself at 07:15).

I do not have any Automator experience, but fiddling with it seems to get me to the point where I'm able to create a collection of all the relevant calendar items, but fail to find out how I can create a logic like: "for each found item: delete alarm; Create new alarm".

Is Automator the correct tool for this and how should I set up the workflow so that it executes the changes to the alarm settings?