Right. I've succumbed.
Here's a snapshot of the latest version of Activity Locking I've been working on.
IT IS NOT FINISHED
Please don't use this on a production server.
I've had to use a zip format called "7Zip" in order to get it small enough to post it on this forum. Do a Google search for 7Zip to find the program to unzip it. It's freeware. Sorry about that, but it's the limits set on Moodle.
There are some brief instructions in the zip, and I'm sure others on this forum would be happy to help if you run into problems.
Hopefully someone with a little more time than me will be able to do some development on it.