VKM1 X MRP

Hi!

In order sales have items with Schedule line category = 'CN' ( VBEP-ETTYP ).

But when I release a free credit (Transaction : VKM1) it should change the VBEP-ETTYP  = "CP" and

execute MRP ( By Transaction : MD04  show in the "Requirements list" ).

  What can I do to execute MRP in VKM1?

Thanks.