cookie on filemaker server

I have an ordering system for 25 science teacher. It is net worked and I want the software to choose the teacher who has opened the app.

I have created a simple tab file with their name (acronym) and when I go Export records using file:Ordering Preferences.tab to specify my out put file it saves it in the Documents file.

However when I try to read this file it cannot find it. I need a default file path because it needs to read the file name on the computer used to open the app. It is effectively a cookie.

I can't make sense of the file paths as described in the help for fole import and export. Using ~ does not give me the root directory either.

If I use the full file path for my computer it works. But that is no good because each person computer has a different hard drive reference number .

Thanks