raise error if material no. doesnot exist

Hi All,

Currently I am checking:

if wa_datatab-col1 is initial

or wa_datatab-col4 is initial

message A000(AR) with 'Error in the file in line,' sy-tabix.

So if my col1 and col4 is blank then it is throwing the error. My col1 is material no. Also I have to throw an error if my materianl no in col1 doesnot exist in mara.

Can anyone of you guys please tell me the code for it.

Regards,

Cheng