Are these Filemaker files hosted by a copy of filemaker or filemaker server that is installed on each server? It sounds like it but if not, that's your first problem.
You can refer to the files by a DSN or an IP address (The IP address can't change, it has to be static.)
A simple way to connect is to simply click New, then click Add File..., Click the remote button and then connect to your file just like you would using Open Remote from the file menu.
You can also do this from other parts of the database. In Manage | Database | Relationships to link a table occurrence to a data source table in an external file, in button set up to perform a script in an external file are two common places where you'd do this.
Thanks for the help again Phil. You are the best.