Control display fo custom field

Hi,

We are on SRM 7.1 ECS.

We ahev a requirement to create a custom field under BASIC DATA tab in shopping cart screen but we would like to display this field only if the item is a service item.

In SRM 5,we had to implement the badi BBP_CUF_BADI_2 for the same reqt.

But in SRm 7,how do we implement this?

Thanks.