How to track customer origin only once during registration on Shopify?

Hi,

We want to know where our customers come from on Shopify.
That’s why in the registration form we add the label “Origin:register”, in the newsletter form “Origin:newsletter”, in the contact form “Origin:contact”…

But we would like this tag to only be saved the first time. In other words, if the user has the “Origin:…” label, do nothing and if not, add the corresponding one.

Would it be possible?

Thanks