How to track business process that goes through different domains in an iframe?

[mmartinezcampos]

What is the best practice for tracking a business process (user registration) that goes through two domains? The initial step is firing correctly on the originating site, but the next step takes place within an iframe loaded from a different domain. The second domain doesn't have the SAS embed tag. From what i've read, it's my understanding that if it was embedded, rules would have to be created to prevent duplicate events. 

We're using DTM to inject javascript for rules that can't be accomplished through the SAS UI alone so i've been researching using Window.postmessage and how to listen for events in an iframe.  Any help is appreciated!

Thanks,

Michael