Hi Chetan,
Below code snippet should work. And also make sure your validations are done in CHECK_BEFORE_SAVE method of order_save BADI.
MESSAGE e000(MSG_CLASS_NAME) WITH 'Error message description:'
ls_orderadm_i-number_int
INTO dummy.
lr_message ?= cl_bsp_wd_message_service=>get_instance( ).
lr_message->add_message( iv_msg_type = 'E'
iv_msg_id = sy-msgid
iv_msg_number = sy-msgno
iv_msg_v1 = dummy ).
lv_err_flg = 'X'.
IF lv_err_flg = 'X'.
RAISE do_not_save.
ENDIF
Regards
Himayat