Disallow PO Box Address

-- url of the page with the problem -- : www.baycitycargo.com
-- HikaShop version -- : 2.3.0
-- Joomla version -- : 3.2.3
-- PHP version -- : 5.3.28
-- Browser(s) name and version -- : Firefox 28.0
-- Error-message(debug-mod must be tuned on) -- : None

We only ship via UPS and therefore can not ship to P.O. Box #'s. How can we disallow the use of a P.O. Box # in the address field? I've searched the site, the forum, manually look through 20 pages of posts in the shipping forum and searched on Google but haven't been able to find anything like this.

Awesome, didn't even know that existed. Thanks!

Can the system be set to allow a P.O. Box for the billing address but not for the shipping address?

Is there an updated version of this that disallows UPS shipping methods based on whether PO Box is present?

One of our clients ships both USPS and UPS. She wants to allow PO Box address for USPS, but not display UPS as a valid shipping option if a PO box is the shipping address.

We can always customize her checkout, but I figured I would ask first to see if anything like that already exists.