How to restrict Winscp users to specific directories

How can we restrict user access with WINSCP to only specific directories.

Here’s the setup, we have an application that writes files to the following directories:
(The application owner is “applVET” with “dba” group)

Ex of directories:
/u1/../APPVET/data/PPS/recv/pps.txt
/u1/../APPVET/data/PPS/proc/pps.txt
/u1/../APPVET/data/VPT/recv/vpt.txt
/u1/../APPVET/data/VPT/proc/vpt.txt
etc..

These directories are owned by the application owner “applVET” with “dba” group.
Ex:
ls –lrt /u1/../APPVET/data
drwxrwxr-x applVET dba PPS
drwxrwxr-x applVET dba VPT

The WINSCP users are connecting via a user called “extr”, this user “extr” is part of the “dba” group to be able to read and write from those directories. The WINSCP users that deals with PPS files extract the files from the PPS ‘recv’ directory, makes modifications and put it into the PPS ‘proc’ directory, the users that deals with the VPT files do the same but using the VPT directories. But we want the users that deals with PPS.txt files to only have access to the PPS directories and the users that deal with VPT.txt file to only have access to the VPT directories but since the “extr” user is part of the “dba” group to be able to read and write from those directories, these users have access to both the PPS and VPT directories.
Is there a way to restrict the WINSCP PPS and VPT users to only specific directories?
Thanks

That's not a question for client. That's about configuration of your server.

As at an appropriate site. Like https://superuser.com/

Thanks, maybe I did not explain it properly. I was hoping that the WINSCP client could restrict the user to a specific directory. So if we create a WINSCP.ini file that contains a specific user and a directory, that this user could ONLY access the directory specificed in the WINSCP.INI file. I was hoping that there was a setting in the WINSCP client that would prevent the user to see any other directories other that the one specified in the WINSCP.ini file.
.
Is this feasible ?
.
Thanks

That would be useless. What would prevent your users from changing the winscp.ini to bypass the restriction?

All our users use the same central WINSCP.ini file, it's setup as READONLY, only admin can change this file .
Thanks

What does prevent your users from using a different INI file?