Hi guys and girls

I wonder if anyone can help.

My store sells wines and spirits and I'd like to make sure that when customers sign up using the login page, that they are over 18 as that's the current law in the UK.

It strikes me that I could do with validating their age when they first sign up, to make I'm covered should I be accidentally selling alcohol to a minor.

Is there a way of:

1. validating the age via the admin panel - I've had a look and can't find any way to do this; or

2. validating it on input i.e. if age=under 18 then throw up an error message / warning, otherwise let them register?

Any help with this would be greatly appreciated!