Hi @dashawk
Thanks for the screenshot. I understand the question now.
This is far to custom to include into the core im afraid. That said, it would be possible for you to write some custom code to do this for you.
I would add a function to the wp_head action which would append some jquery to the page. You could query the DB for the amount of posts with this checkbox value (see docs for querying), then depending on the value, you could generate some jQuery to either remove / hide or disable the checkbox field.
All up, it should only take 30 minutes or so.
Good luck
Thanks
E
