Here is some SQL to extract the current users:
select distinct DB_NAME(dbid),loginame, dbid
FROM sys.sysprocesses
where [dbid] not in(0,1,4) -- exclude list
Note there are two levels of security in SQL Server - SQL Security and "Integrated" security. The latter uses the windows login, SQL Security is managed by you within SQL Server. It looks like you intend to add an SQL user/login named for the branch with a defined password that everyone in the branch will use. Not a great idea IMO. You can use integrated security and add each windows user to SQL server and then add the SQL users to security groups to control access to the SQL objects. This would require each user to authenticate with your windows servers first locally before they can connect to the remote server.
I'd highly recommend you upgrade to at least SQL Server 2008 R2.