BP Search by Tax Number

Hi Gurus,

i got the following requirement: the research of a Business Partner in the CRM server cshould be possible through the tax number (VAT number).

As far as i understood it's not part of the standard search helps we have for BP in the different transactions.

Which would be the alternative? Modifying the standard search help to enhance it with tax number field? Would it be a modification of the standard or does it exist any BAdI for that.

Thanks

C*