Classic group automatically add objects

Hello,

I try to add a newly created hatch of an existing Classic group with Lisp in the following order:

There is a closed polyline. This belongs to a group.

Now I create a hatch in this closed polyline by clicking within the border.

My goal is to use a lisp to add this hatching automatically to the group which also belongs to the polyline.

The Lisp should check whether the border of a Classic group belongs and if so add. If no then output a warning.

How could I realize this?

Please help.

Martin