Additional (custom) field in Easy Cost Planning (ECP)?

Would it be possible to add an additional (custom) field in the standard entry screen of Easy Cost Planning (for example using a BADI or otherwise)?

Relevant transaction = CJ20N or CJ9ECP: entering ECP for WBS elements.

We would like to add some specific data to each line item in the Easy Cost Planning (reference id to other structure views).

Thanks,