How about Kiosk Mode?
Argh RTFM Me !
You're spot on Malcom, for some reason I though kiosk was only for iOS (I think I got confused by iOS's kiosk)
Thanks a lot !
Just to add a little Mac finesse to this approach, if your "Kiosk" is a true single user - don't touch the OS kind of application, you can run the solution under a Mac "manage with parental" user account setting and launch into that account on startup, launching the filemaker file on startup, you might also want to create custom menus to restrict user actions...?