Passing data into Velo from external Javascript

I am trying to integrate a 3rd party Javascript Library with a Velo form but have run into a roadblock.

The Javascript library is not on NPM and is embedded in the page as custom code. It cannot be included wholesale in Velo as it needs access to the document and window objects to function. It loads on the page fine but there appears to be no way for the library to communicate with a form inside of Velo or for code inside of Velo to access any data from the external Javascript Library.

Is there any way to pass data into Velo from external Javascript that I have missed?

Step-1: Get the external data you need on the page (front-end or backend).
Step-2: Push the recieved data from your wix-page to your HTML-Comp. or Custom-Element.
Step-3: Start your code inside Custom-Element (first loading the recieved data from Wix-Page) —> now you are able to use the data inside the Custom lement.