Hi,
Please try below logic.
DATA: L_S_MC13VD0ITM LIKE MC13VD0ITM.
When '2LIS_13_VDITM'.
LOOP AT C_T_DATA INTO L_S_MC13VD0ITM.
L_TABIX = SY-TABIX.
SELECT SINGLE PERIO FROM FPLA INTO L_S_MC13VD0ITM-ZZPERIO
WHERE FPLNR = L_S_MC13VD0ITM-VBELN
MODIFY C_T_DATA FROM L_S_MC13VD0ITM INDEX L_TABIX.
ENDLOOP.
WHEN OTHERS.
EXIT.
ENDCASE
Thanks
Ganesh Reddy.