Group based on Custom Field

Not sure why this topic got “automatically bumped” after two years, but it’s timely. I would use such a plugin. I have investors who need to self-certify that they meet certain criteria before they can see the private category. Right now it’s a manual process- they send me a private message saying they meet the criteria, and I manually add them to the group. It would be great if they could self-certify by ticking a box.