Vendor Field Status - changing based on Purch.Org.

In R/3 4.7 Enterprise we have set the Vendor Field Status Groups for the Account Group in configuration. In the Vendor Master data Address screen the 'Street' field is set as mandatory/required. This is fine for the majority of vendors, however, for certain Purchasing Org's we would like this field to be optional.

Any ideas how to achieve this? I have searched for a suitable BADI or function-exit but to no avail.

Thanks for any help.

JB