Preventing form submission based on option slected

Hello,

I've created a form with many fields on it, however I'd like to prevent the user from proceeding and submitting the form if a certain option is selected/not selected in one of the first dropdowns.

For example, you could have a dropdown like "Do you really want to submit this form? | Yes / No", and if No is selected, we do not display any remaining fields, and don't allow form submission.

I tried using conditions, but I could only selectively "show" the remaining fields below it if the positive option is selected... however this breaks all of the remaining conditional logic further down (bad).

I will probably end up doing it with JS but if there is an easier / cleaner method I would like to know.

thanks