Hide - Block Customer data additional field? (KNA1-KATR6)

Hi,

I shold be to know how can i hide/block the editing by user with the VD01 or VD02 of one field on additional data. The field is KATR6 (KNA1). The user that log-in on Sap system should be for example create a new customer (with VD01), inserting all the necessary info for the creation, but: if he should be decide to go to the additional data menu, I need that he cannot be able to edit (or change in case of VD02) the KATR6 field.

How can I do?

Thanks a lot

D.