Filter registered from a grandchild node in a book by an Entity Reference in Views?

I really like this module - it gives the end user god ability to overview and keep control in a node level view!

Before I used "SignUp" but I think this gives more future abilities.
But in "SignUp" I was able to filter Paren-parent "Signups" in a book from a child-child-node in to a "Entity Reference field" from one Entity Reference pane made in views.
In Views Entity Reference pane I was able to collect and filter a registered signups from a parentparent book page and then able to choose between only registered user in a list and pic one of them in the child-child-page-field.

Look at it this way: Each user have a dog. Each user can registrer the dog to an event by using "Entity Registration".
And I want to collect between the registered dogs names in the child child enity-reference-field so only dogs names who is registred in the parent-parent-node is visible in to the Entity-Reference-field .
(Dogs are available in different breeds - The breeds is the parent nod to the child ore the child node to the book level where you do the registration - but nothing else happens here)
(There is also many different parent-nodes who will collect Registrations for other events, by that it's important to keep users dog name apart and invisible for other user who do have dog entered in the specific event.)

But, I don't understand how to do it with Registration ?

I have try with one views view from "Registration" who filtering and collect all the "Registred" from respectly node ID where from the user do the registration to/from (node/%/node - view). I have also tried to start witha user-wievs-view, but can't fin a good way to enter relation to the node and Registration-user so I can filter them to the level I need.

I want to collect information "only on registered user to that specific event" (in the paren-parent-book-node) through the Entity Reference pane in to a child child pages entity-reference-field. The problem is that I need to filter the user so only registred user are choosen and then collect data from a field in the user node so that shows in select field (child-child-field), and show the user name or ID (they are invisible).

(There is also many different parent-nodes who will collect Registrations for other events, by that it's important to keep users dog name apart and invisible for other user who do have dog entered in the specific event.)

I hope to avoid the "reference" module and instead go trough "entity Reference" module to fix this issue.

To do what I want I probably need to create relation between Book levels, user, Registered users and nod ID. But I can't figure outh on how to do it - from type of views shall I collect the relations?

Please anyone - How to do this?