[Solved]Controlled fluid connection

[Linver]

Hi all!
I have a problem and I dunno the best method to do it. I want (is not the real problem but is the same) create a prototype A with some fluid box connection, and I want that all entity of prototype A will connect only with other of the same types or with a list of type. Is possible do this check? And do it only for one connection of multiple connection of prototype A? (one side)