I have searched all over the FAQs and forums, but need the correct php code to limit the zip code that can be entered.

I know it is a simple "IF" statement, but I'm new to php & ZenCart and just need a little direction and help.

What I would like to do is have an IF statement so during registration if the do not not enter XYZ or ABC zip code, they would get an error saying something like, "Sorry we currently only serve XYZ and ABC zip codes".

Thanks in advance for your help!