CRM Bp TRX Doubt about validation field TAX NUMBER tab Identification

Good afternoon,

I have the following problem, is required to make a validation on the Tax Number field in the Identification tab. I searched for Badis or exits without success.

Anyone knows if there is any other way to do this validation? I meant, maybe there is any trx where some fields validations are include

I know little or nothing of CRM.

Any help is welcome and if there is some missing information please let me know,

Thanks a lot,

Sorry for my english

Tulio G.