how to make a field mandatory in SAP Business one

Kindly help on this...SAP B1 9.0  HANA 

IF :object_type = n'2' AND (:transaction_type = n'A' OR :transaction_type = n'U') THEN

    declare BP_M_RM_PM varchar(100);

        SELECT

        (SELECT OCRD."CardCode"

        FROM OCRD

        INNER JOIN OUSR OUSR ON OCRD."UserSign" = OUSR."USERID"

         WHERE OCRD."UserSign" NOT in ('2') and OCRD."GroupCode" in ('102','101') and OCRD."CardType"='S'

       AND OCRD."CardCode" = :list_of_cols_val_tab_del AND IS NULL(OCRD."Cellular", '') = '') INTO BP_M_RM_PM FROM DUMMY;

        IF :BP_M_RM_PM > 0 THEN

            error_message := 'Mobile Phone cannot be blank.';

            error := 12;

        END IF;

        END IF;

Error:

  [SAP AG][LIBODBCHDB32 DLL][HDBODBC32] General error;383 invalid identifier: POHead: line 3 col 6 (at pos 286)