Hi!
I am working on a ConfiForms form and using a multiselect field there.
We have a requirement to restrict the user's choices to exactly 3, meaning a validation should throw an error "please select exactly 3 options".

Unfortunately we are limited to the built-in functionalities of ConfiForms. I cannot use any custom user macros. Neither can I use a CSS or a HTML macro.
Is there a way to achieve this within the ConfiForms validation rules?
Thanks for any help!
Best regards,
Roman