Hi Sar,
I am giving you a sample code. This should work for you.
DATA: ls_logical_key TYPE crmt_partner_logic_partner_key.
lv_ref_guid = guid of order.
lv_pfct = '00000052'.
* Read order to fetch existing partners
APPEND 'PARTNER' TO lt_req_obj.
APPEND lv_ref_guid TO lt_hdr_guid.
CALL FUNCTION 'CRM_ORDER_READ'
EXPORTING
it_header_guid = lt_hdr_guid
it_requested_objects = lt_req_obj
IMPORTING
et_partner = lt_partner_wrk
EXCEPTIONS
document_not_found = 1
error_occurred = 2
document_locked = 3
no_change_authority = 4
no_display_authority = 5
no_change_allowed = 6
OTHERS = 7.
CHECK sy-subrc EQ 0.
REFRESH lt_input_field_names.
ls_input_field_names-fieldname = 'DISPLAY_TYPE'.
INSERT ls_input_field_names INTO TABLE lt_input_field_names.
ls_input_field_names-fieldname = 'KIND_OF_ENTRY'.
INSERT ls_input_field_names INTO TABLE lt_input_field_names.
ls_input_field_names-fieldname = 'NO_TYPE'.
INSERT ls_input_field_names INTO TABLE lt_input_field_names.
ls_input_field_names-fieldname = 'PARTNER_FCT'.
INSERT ls_input_field_names INTO TABLE lt_input_field_names.
ls_input_field_names-fieldname = 'PARTNER_NO'.
INSERT ls_input_field_names INTO TABLE lt_input_field_names.
CLEAR: ls_partner_com, ls_logical_key, ls_input_fields, ls_partner_wrk, lv_ref_guid.
ls_input_fields-ref_kind = lv_ref_guid.
READ TABLE lt_partner_wrk INTO ls_partner_wrk
WITH KEY partner_fct = lv_pfct
ref_guid = lv_ref_guid
ref_kind = 'A'.
IF sy-subrc = 0.
MOVE-CORRESPONDING ls_partner_wrk TO ls_logical_key.
MOVE-CORRESPONDING ls_partner_wrk TO ls_partner_com.
ELSE.
ls_partner_com-ref_guid = lv_ref_guid.
ls_partner_com-display_type = 'BP'.
ls_partner_com-no_type = 'BP'.
ls_partner_com-partner_fct = lv_pfct.
ENDIF.
ls_partner_com-kind_of_entry = 'C'.
ls_partner_com-partner_no = new employee responsible.
INSERT ls_partner_com INTO TABLE lt_partner_com.
ls_input_fields-ref_guid = lv_ref_guid.
ls_input_fields-logical_key = ls_logical_key.
ls_input_fields-objectname = 'PARTNER'.
ls_input_fields-field_names = lt_input_field_names.
INSERT ls_input_fields INTO TABLE lt_input_fields.
CALL FUNCTION 'CRM_ORDER_MAINTAIN'
EXPORTING
it_partner = lt_partner_com
CHANGING
ct_input_fields = lt_input_fields
EXCEPTIONS
error_occurred = 1
document_locked = 2
no_change_allowed = 3
no_authority = 4
OTHERS = 5.
IF sy-subrc EQ 0.
CALL FUNCTION 'CRM_ORDER_SAVE'.
CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'.
ENDIF.