scripting filemaker preferences

i am trying to access filemakers application preferences from within a database called change user name. what the scrip within this database will do is bring up a custom dialog and allow a user to select a new username, type it in the dialog which has a global field and copy the name. what i would like to happen from there is an applescript to paste that name into the applciation preferences under custom username. once that was done, the filemaker script would launch a timeslips db and user db where the user would securely log into the system. the database and security model exist already, i just want to provide users an easy way to change their login name which is based on the custom username in filemaker’s preferences.

i started to write this and got stuck. i couldn’t seem to find how filemaker under os x addresses the menu location of the preferences. i was using script debugger and found all the menus but that one.