Hello Maren,
Lt_header_guid is a table.
Declare the following:
TYPES: begin of guid_typ,
guid type crmd_orderadm_h-guid, "this must of type lt_header_guid-guid
end of guid_typ.
DATA: lt_guid TYPE table of guid_typ,
ls_guid type guid_typ.
Assign the guid to ls_guid work area.
Then append ls_guid to lt_header_guid.
Lt_header_guid table goes to CRM_Order_read FM.
Check the table CRMD_ORDERADM_H for the service request