Whats the best way to save a default folder location that is user specific?

We have macros that save files as PDFs, DXFs, and std SW files.  Each user saves files to a specific project folder they are working on.  I thought about using an excel sheet to save these folder locations but what happens if 2 users tries to write to that file at the same time.  My second thought would be to create a simple TXT file to save the folder location, each user would have their own TXT file.  The user wouldnt have to worry about these files, since they will be managed by the macro.

Any suggestions/tips?

Ex.  username: jblow is logged into the system

jblow saves:

PDF files to C:\ProjectXYZ\PDFs

DXF files to N:\DXFs\jblow

SW files to C:\ProjectXYZ