Drupal Commerce USPS Module: Disable Shipping Services If Product Option Exists
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I need to disable all but one USPS shipping service (Parcel shipping) if any product in the cart has a certain custom product option (a checkbox) set.

I am a very good with Wordpress, but I am new to Drupal and cannot find a way to make this work.

What I've been trying is to set data comparison condition rules on each rate that I don't want to be available (Priority Shipping, etc). However, I can't seem to drill down to the products in the cart in order to check the product field value since I only have site: and commerce-order: root selectors available.

I am working with the latest version of Drupal and Commerce and USPS shipping modules.

Thanks for any help or direction!
