Required field in conditional group

Hi everyone,

I’m working on a form in which I need that if the user select an option in a dropdown an acceptance field will appear. I need to that this field has to be required. The problem is that I also need that the form can be send even if the voice selected in the dropdown is another and the conditional field will not appear. How can I make the field required only at the condition that the related option in the dropdown is selected? Is it possible?

Thanks.