How to use mmpur_remove_msg_by_context in PROCESS_PO_CUST-CHECK

Hi all,

I have use this code for set custom messge to messgae log po :
for item messgae

" add new message<br>mmpur_business_obj_id ls_item-id.<br>mmpur_message_forced 'E' 'ME' '303' ls_item-ebelp 'Tax tariff code : 18' sy-msgv3 sy-msgv4.<br>iv_failed = abap_true. <br>ls_items-item->invalidate( )<br>

"delete message by item<br>mmpur_remove_messages_by_id ls_item-id.<br>

for header message

" add new message<br>mmpur_business_obj_id eo_headerid.
mmpur_message_forced 'E' 'ME' '303' TEXT-002 sy-msgv2 sy-msgv3 sy-msgv4.<br><br>" delte message by header<br>mmpur_remove_msg_by_context ls_header-id ''.<br>

successd to display a custom message and to delete it.
but the save pop-up in po ( ME21N, 22 ) not appear, and nothing happen when I click save button at top.

what's missing in the code?

* I've used several methods in several tutorials, but still not working