Badi ME_PROCESS_PO_CUST not triggered when PO Z header field is changed

Hi guys,

We try to implement Badi ME_PROCESS_PO_CUST for updating PO header text.

We've created a custom field in EKKO and on ME21N (PO creation) we're maintaining a value in it. When pressing ENTER, the Badi ME_PROCESS_PO_CUST is not triggered.

How can we trigger the method 'Process_Header' of Badi ME_PROCESS_PO_CUST after changing the PO custom header field?

TIA,

Limor