Receiving variables from external applications

I have a few questions about how I can receive variables from external resources. I am running a few layouts via the Instant Web Publishing interface. It is a scholarship application for students in my department. The file is served up with Filemaker Server 8. The student will simply click the link and a startup script limits access to most options except data entry.

Currently I have them entering their own Student ID # (which I use as the unique ID), however, this doesn't prevent them from accessing other students records.

I have the potential option of receiving information from and LDAP server or via java script...for instance, they would log in using the University's Login/Password interface, after which the server could send variables/parameters to Filemaker such as their Student ID#, Name, etc. from the University's records.

My question is how exactly Filemaker receives these variables, parameters, etc.? And does special consideration need to be taken since the file will be accessed via the Instant Web Publishing, and since multiple users may be accessing the file at once?

Thanks for any and all suggestions!