SQL & PL/SQL :: Data Manipulation Insert - Procedure / Trigger Should Delete Initial Record Saved

i have one table ot_ins_item where user will enter the details of item, grade,item qty , later on user will go and update the same table the details of different grades received for the same item in different columns with qty breakup in 3 different fields it_qty_01 , it_qty_02,it_qty_03 respectively with different grades , what i need is i want is whenever he updates this table with different grades based on data entered in 3 different fields , a procedure or trigger should delete the initial record saved and insert three different rows based on newly updated values , it may be 3 or it may be 2 sometime depending upon input values that many records should be inserted same time controlling the qty's entered in breakup not exceeding the main qty.

CREATE TABLE ot_ins_item (it_ins_no NUMBER,it_no NUMBER,it_grade VARCHAR2(12),
it_code VARCHAR2(12),it_qty NUMBER,it_flex_01 VARCHAR2(12),
it_01_qty NUMBER,it_flex_02 VARCHAR2(12),it_02_qty NUMBER,it_flex_03 VARCHAR2(12),
it_03_qty NUMBER);

create sequence s_it_no start with 1 ;

INSERT INTO OT_INS_ITEM VALUES (1,s_it_no.NEXTVAL,'A','ITEM1',NULL,NULL,NULL,NULL,NULL,NULL);
INSERT INTO OT_INS_ITEM VALUES (1,s_it_no.NEXTVAL,'B','1TEM2',NULL,NULL,NULL,NULL,NULL,NULL);
INSERT INTO OT_INS_ITEM VALUES (1,s_it_no.nextval,'C','ITEM3',NULL,NULL,NULL,NULL,NULL,NULL);
SELECT * FROM OT_INS_ITEM;
[code]....