BUILActivity BOL Object Modification

Hi Experts,

I have a requirement, in which I want to add an extra field to BUILActivity in BP_BPBT UI, but AET is not providing me the feature Add new field there, so I checked in AXTREG Tcode it is not registered there. In EEWB the BUILActivity Business Object is not available. How can I add the field to it?

Thank and Regards,

Nikhil Kulkarni