FM Advanced Q

I have a number of db's running on FMSA and don't want to issue a direct
link to them nor do I want them to show up in the available database list.

What I would like to do is this:
User enters url in browser and goes to a welcome page. Within the welcome
page, it asks for their account number. User enters their account number,
clicks submit. Based on the account number entered, they would then be taken
to the correct db page to login for their db. The account number would be
prefilled from their previous page so all they would have to supply on the
FMSA login page would be their password.

Is this possible and any suggestions on how to accomplish this??

Thanks in advance for any help or guidance!