Automator and iCal: Hide calendar alerts?

Hi.

I'm using iCal to schedule and automatically execute an Automator workflow at a given interval by telling iCal to "open file" as the alert for my event. It works great, but what I'd like is to have the iCal alert hidden when the alert goes off so that I don't see it on my desktop. After all, the whole point of the automatic workflow is to have things done without me having to lift a finger, so it annoys me a little that I have to click dismiss each time the alert comes up.

Choosing "ignore alerts" in the calendar info in iCal disables the alert (and thereby the execution of the workflow) entirely, which I definitely don't want.

Is there a way to hide the alerts so I don't have to see them but still have them "go off" and thereby execute the workflow?
Of course, I'm also open to other solutions than Automator and iCal. My workflow is a really simple one consisting in emptying the contents of one folder and then copying files from another folder to the emptied folder.

- Thanks!

Oh, and also: I'm using OS X Mavericks.