User Hook - POR_CUSTOM_PKG

Hello

How to catch and throw an error to user when the validation fails in iProcurement page using User Hook package POR_CUSTOM_PKG

As per Doc ID 1942913.1, point number 9,  If the data does not comply with your requirements, you may throw an error advising which data needs to be manually corrected by the user before proceeding and completing checkout and submit.

if anyone having experience with POR_CUSTOM_PKG and throwing error back to user page, please provide insight or help.

Regards