Ultimate Form Mail comes with a few standard field checks already in place but it also gives you the ability to create your own custom field checking formula.

Here's a 6 minute tutorial:

http://www.ultimateformmail.com/help-movies/field-validation.php

When I created Ultimate Form Mail I knew that my clients would want to validate fields for security and other reasons... but I also knew I had to build flexibility into the system to account for different formats.

For example, a field checking formula for telephone numbers in the United States would fail miserably for phone numbers overseas (UK, Australia, Canada, etc, etc).

But with this tutorial, you'll know how Ultimate Form Mail check field values, and how you can set up your own functions.

If you're not a coder, I give you three or four resources for getting the code you need very inexpensively.