line item wise error message in ME_PROCESS_PO_CUST

Hi team,

i have a requirement to display error messages in line item wise if the enetred line item tax code is wrong . Below thread is most usefull but i have followed the same. it i working fine if i insert wrong line item , it is showing me an error message in line item , if i correct the same with right entry still the error message resides on line item.

Below is the thread which i have followed and piece of code which i have used.please suggest me where i'm going wrong

https://archive.sap.com/discussions/thread/1193200

lv_text = 'Invalid Tax code'.

if wa_taxcode-zzmwskz = mepoitem-mwskz.

INCLUDE mm_messages_mac.

mmpur_message_forced 'E' 'ME' '083' l_text ' ' ' ' ' '.

CALL METHOD im_item->invalidate( ).

CONTINUE.

ENDIF.

thanks in advance.