User Exit in MIRO

Hi Everyone,

I need to validate the item tax code and pass an error message to the header level custom field.

I am using MM08R002 and fn module EXIT_SAPLMR1M_001 it is triggering when user is selecting any line item in the po and try to save it ..

The problem here is when I throw the error message, the header level fields fields are non editable. I need the header level fields editable and validate the item data.

Please suggest ideas.

Thanxs

regards

vijay