BAdI ME_GUI_PO_CUST with custom table in header tab ME23N

Hello guys,

I got the problem that my custom table in header tab of ME23N transaction is not showing up. I know there are many questions here about this, but in my case I do not have any custom field in CI_EKKO. I only want to display a custom Z*-Table as ALV grid. So I do not know how to put any mapping of fields because I do not have any fields in the tab. Maybe this is the problem? How can I put an ALV Grid table in ME23N custom header tab.

Regards

Michael