I need a good query to cull/remove a specific message from the activity log

I realize this isn't the right place to ask, but I can't find a user forum.

I do a daily calendar update which shows up as hundreds of posts in the activity log. It makes it very hard to see other events I'd like to monitor.

As there is no way to exclude them in the displayed output, I was hoping somebody could suggest a query I could use against the database to delete those?

... my current work-around is to upload as CSV, then sort in a spreadsheet, and delete those rows.