Define the same account name and password in each file. Use a script with Open File to open each of the other files.
Use FileOptions to specify an account name and password be auto-entered when the file is opened. THis can be a very limited access password. A script in each file can then use "Relogin" to open the file with a specified account name and password--which can be passed in a script parameter from the first file.
PS: This is one of the "cons" to having a multiple-file system. If you had all your tables in one file, this complication does not occur.