Creating a purchase 'requirement' in Shopify, before customer can be added to CRM?

We are trying to figure out a method where if we invite a new customer to register an account within Shopify, they won’t actually be added to our CRM system as a ‘fully qualified’ customer until they have actually made a purchase (versus just registering an account in Shopify).

Would this be most easily done with Shopify Scripting, or is there a built-in feature that would enable such a function?