Validation on Save is not working for extension BO GAF screen

hi

please help me in this ASAP.

in my requirement i have to set an error message for an extension field. the code i wrote is working for Custom BO but not working in GAF screen of that standard BO. I tried everything possible but not getting any solution

[probable reason = the standard BO "PSM write access allowed- NO" (Not sure about it.)]

In My extension BO i wrote the “Adhaar card number only have 12 digit” and “Bond Start date is not grater than Bond End Date” for raise error message. i tried them in Validation onsave then Even Aftermodify as well as Event Beofesave. but i observed that the raise error message is not working in Business object extension named “PersonnelHiring” NS- AP/PersonnelAdministration/Global .

in the same time i also tested the scripts for another customized BO and it is working. So i am unable to find the reason for not working error message in my given Standard BO.