Set up IBAN number of vendors as a sensitive field

Hello,

We are on ECC 6.0 and we want to set up the IBAN Number as a sensitive field for dual control (Vendors). Currently we only have the bank account as a sensitive field so I have entered TIBAN-IBAN in the customzing for defining sensitive fields for vendors. However this doesn't seem to work. Does anybody know exactly how I need to set it up ? Do I need more fields ?

Thanks as ever!

AS