find max value from internal table

DATA : BEGIN OF SUBVBPLP OCCURS   10,

       vendprodid like mara-mfrpn , 

       CUMQUANTITY  TYPE I ,

       PACKLISTID LIKE VBRK-VBELN,

       mfr_id(3) ,         

       debtorid(27),             

       END  OF SUBVBPLP.

SUBVPLP-CUMQUANTITY = 10.

APPEND .

SUBVPLP-CUMQUANTITY = 20.

APPEND.

I WANT TO FIND THE MAX VALUE FORM CUMQUANTITY . AND RESULT INTO ONE VARIBALE . PLS GIVE SUGGESTION TO GET MAX VALUE