Hi Venkat,
Check this code;
IF ( SOURCE_FIELDS-ZMARG1 ne 0 AND SOURCE_FIELDS-ZMARG2 ne 0 AND SOURCE_FIELDs-ZMARG3 ne 0 ).
READ TABLE IT_ZPUR WITH KEY MATERIAL = SOURCE_FIELDS-MATNR
INTO WA_ZPUR.
IF SY-SUBRC = 0.
RESULT = WA_PUR-/BIC/ZPUR_ZCHY1.
ENDIF.
ELSE.
RESULT = '0'.
ENDIF.
Best regards,
Sakthi