Is this possible without scripting? I have a custom record with ZIP and Region fields. On the SO, I have the same fields. When I fill out the ZIP field, I want to automatically populate the Region field on the SO (based on the custom record entries).

You can achieve that usingName field to store the ZIP Code then creating a List/record on SO where the user enter the ZIP (only existing zip code will be allowed) then sourcing Region field value from ZIP custom record linked to ZIP field

The Zip field on the SO would need to be a custom field that references your custom record

Thanks. Sorry, I might have oversimplified the use case. The ZIP Code is not manually populated. It should be based on the shipping address zip code. I was able to filter the custom record list in the SO based on the shipping address zip code based on the filter defined in the custom field. But what I would have hoped is that the custom record field in the SO is automatically populated and not just filtered.