Customize MARC - random updates

Hi All,

I have added a custom field to MRP1 sub screen in MM02/03, through this field I am updating MARC table. For updating I am using exit EXIT_SAPLOMCV_902. The issue I am facing is that it updates the fields randomly, i.e. some times update occurs and some times it is blank. I am updating the MARC table against MATNR and WERKS fields.

It is very urgent issue for us, any help will be greatly appreciated and rewarded.

Thanks in advance.

Regards,

Barjinder Singh.