Raising error message in MIGO for cancelation

Hi Experts,

While canceling line items for a material document using tcode MIGO, I have to raise error message if all the line items are not selected before posting.

for this I am using the line_modify and mode_set methods of badi 'MB_MIGO_BADI' but can't raise proper error message. Is there any other way to raise the same using implicit enhancement. if yes then please let me know where to add the implementation in it.

Please let me know ASAP. It's urgent.

Thanks in advance.

Sanjeev