ESS: Validation Rule on Standard Percentage in Bank details(IT0009)

Hello Experts,

My client required below validation on portal

If an employee opts for Paycard(bank type) and he does not have the Main bank maintained in IT0009, then the system should not allow him to save unless he puts 100% for Paycard. 

The system should display an error message “There is no other bank account maintained. Pls change the % of the amount".

I written the user exit it is working fine on ECC but not reflecting changes on ESS Portal.

Please help me out how should I achieve this.

Thanks & Regards

Prajyot D.