Not sure I understand... if the same account exists in each file then you only need to login once. For each additional file that is referenced, FM will use the same credentials. So your desired behavior is what FM already does...
If you have many files, you may want to look into External Authentication to reduce the amount of work you need to do in account management.
Dear Mr Decorte,
Thanks for the reply, I wasn't aware that filemaker did automatically activate the account when moving from one database to another. I will give it a try.