Pass a variable

Does anyone know how to pass a variable to a custom post template? I can put it in custom fields, or put in the post somehow. I want to have hard posts that use variables for the post template. So say it shows a list of movie theaters in a town, I want to be able to enter the zip code that my post template uses as a variable, but I want to have regular posts for those, not put it as a variable in the url of a single post. Thanks!

https://www.ads-software.com/extend/plugins/custom-post-template/