URL Mapped Detail sub-pages?

[David Bertrand]

Trying to figure out a reasonable way to get this in place. My url-mapped detail pages need sub-pages for just one field. I figured I could create a new content type for that field and relate it to the main content type. Then set the URL Pattern with the urlTitle from the related object. It seems you can't access the related object value when do that though?

eg: /objects/{related_object.urlTitle}/more-details/

Am I overlooking something?