Multiple key pads input, have any one has worked with 3 numeric keypads

Hope to be in the right forum.
Is there a code to real multiple keypads connected to one PC?
In other words, 3 users are entering numbers using 3 keypads.
The issue is how to allocate the input of each user individually.
The program has worked until now by only having to input one digit.
No problem at all. the input field was designed as a one digit field and to advance upon getting a No.
Now I need the same situation, but 3 digit instead of 1.
You can see the problem as user2 for example starts to enter a 7 and user3 starts and puts 6. At the present since there is no isolation, the PC is getting 76. for the first field.
The program can incorporate a c++ code.
Is there a chance here?

You'll need to, on some level, use platform-specific APIs. On Linux, you can probably use libusb, and possibly distinguish between the various USB devices on the computer. Not sure if there's a libusb port for windows.