video 18 or over passgate

I have a site and I notice that more and more adult are adding content I posted private videos but I what I need is a way for adults to post their videos without it being viewed by younger members on my site. I need some type of gate for members to confirm ther are 18 to see the other videos. even if its a simple click here if you ar 18 button or leave if you are not 18 button but I dont want to videos to be accesiable by all members just th ones who want to view it. Does anyone know of a mod or way to create this?