I don't think I got your question clearly.
You are creating a unique serial number using some application in the PC and you are trying to assign this to USB device?. Or
Are you trying to read the serial number of USB device from the host application?
I want to read the serial number of USB device from the host application.
Also I want to read the UID/PID/Release Number of usb device from the host app.
Sorry for my poor English.
Install Cypress SuiteUSB from the below mentioned location:
Refer cydesc host application example (C:\Cypress\Cypress Suite USB 3.4.5\CyAPI\examples\cydesc).
Also, please go through the CyAPI.pdf.