How can a user only set a single checkbox

I am a CB 2.0.5 professional user on Joomla 3.3.6

I want to create a situation where a user can set a (single) checkbox; after the chckbox is checked this user cannot uncheck it anymore.

Is it possible to create such a situation by means of CB Auto Actions, CB Conditional, or CB Query ?

I think I am looking for a way to change the "read only" state for this field/user combination to YES

You could make it read only. They'd then be able to check it during registration, but won't be able to during profile edit. The alternative is you could try conditioning its own self and hiding if its value is equal to 1 using CB Conditional, but this could cause a very strange loop.

Ideally you'd just set the field as Required. They'd be required to check it and they won't be able to uncheck it as they wouldn't be able to then update their profile.

Sorry, just don't understand the need for this without further explanation as to what you're trying to do.

Thanks for your reply. Yes it is a little bit stainge. Let me explain.
We decided all users should allow automatic incasso of their club contribution. So members are allowed to set OK for that but should not be able to reset it after that.

I tried the hide condition but I was not able to hide it also in edit mode. In some way the hide in edit mode does not work for CB Confitionals. I also noticed that for other conditions. Is this a known issue or do I do something wrong?

CB Conditions works perfectly fine, but a fields own value conditioning it self is really weird and may not behave right. You need to first ensure CB Conditional is up to date though (latest being 4.0.5). I'm not sure what more to advise though as it's a really weird scenario. CB Conditional should be able to cover it, but I've no idea if it'll work with a field conditioning its own self.