Nancy, thanks for the reply.
Using associations requires the user to upload each related document to the repository first, and then add them to my custom content.
The related documents would be loose coupled objects whereas I want to have them tightly coupled when creating them in my content.
I'd like to have the related documents "not visible" elsewhere but in the content that I created.
No other content, even content of the same custom content type can relate to the same document.
best regards,
Ryan