I need to be able to validate is someone is over 18 years old based upon their date of birth and a date in the future.

Is this possible?

Hello Kelvin Wright.

It's possible applying rules to the field . I think the following video can be helpful in order to what you are trying to achieve :

Validate Minimum and Maximum selected items with Universal Form Validator ASP

Take a look also on our other videos in which we explain the functionality of the extension :

Universal Form Validator ASP Videos

Also our manual section explains very user friendly how to use the extension:
Universal Form Validator ASP Manual