You would have to create a page with a data view. Then you pass the parent object to the page, and set the data source of the data view to “Association” and select your parent NPE. Then place a list view or a data grid inside the data view. Select “Association” as your data source again, and navigate the object tree to your child object.
The data from the variable can not be passed directly to a page. You would have to add an attribute to one of your NPEs, or create a new NPE (and associate it to the existing ones), and then fill that attribute with your variable value.