Now it is working fine,there was a problem with logic,
FORM FRM_KONDI_WERT_901.
*{ INSERT IRDK900244 1
DATA: WA_XKOMV TYPE KOMV,
V_ZAMT TYPE KBETR,
V_ZAMT1 TYPE KBETR,
V_ZVAL TYPE KBETR value '100.00',
V_ZTOT TYPE KBETR.
READ TABLE XKOMV INTO WA_XKOMV WITH KEY KPOSN = XKOMV-KPOSN
KSCHL = 'ZFNN'.
IF SY-SUBRC = 0.
V_ZAMT = WA_XKOMV-KWERT.
ENDIF.
READ TABLE XKOMV INTO WA_XKOMV WITH KEY KPOSN = XKOMV-KPOSN
KSCHL = 'ZVAT'.
IF SY-SUBRC = 0.
IF V_ZAMT IS NOT INITIAL AND
WA_XKOMV-KWERT IS NOT INITIAL.
V_ZAMT1 = V_ZVAL + WA_XKOMV-KBETR.
V_ZTOT = V_ZAMT * WA_XKOMV-KBETR / V_ZAMT1.
CLEAR : XKOMV-KWERT.
wa_XKOMV-KWERT = V_ZTOT.
xkwert = wa_xkomv-kwert.
MODIFY XKOMV.
ENDIF.
ENDIF.
Now it is good.