How to update the number of records using for loop in oracle / pl SQL

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SQL

Oracle

trigger

Hi, Professionals
hope all of you are good.
i am new to oracle and PL SQL, i want to update the received item in stock in previous date by using for loop. i want that when i press the button it will update the record of the given date and id of a specific product and also update the records in next date prior to the maximum date in the table. please check the below code in when-button-pressed trigger. everything is working fine but the update statement does not do anything.
please help me to get me out of this stuck.

What I have tried:

DECLARE 
	DATE_DIF NUMBER;
	MAX_DAT DATE;
BEGIN
	SELECT MAX(DATED) INTO MAX_DAT FROM STOCK;
	 DATE_DIF := MAX_DAT - :TEXT_TOP_DATED;
	
	FOR CNT IN 1..DATE_DIF
	LOOP
		SELECT OPENING, RECIEVED , CONSUME, CLOSING,DATED INTO :OPENING, :RECIEVED, :CONSUME, :CLOSING, :DATED FROM STOCK WHERE DATED = :TEXT_TOP_DATED + 1 AND PRODUCT_ID = :LOV_PNAME;
		:CLOSING := ( :OPENING + :RECIEVED ) - :CONSUME;
		UPDATE STOCK SET RECIEVED = :RECIEVED, CONSUME = :CONSUME , CLOSING = :CLOSING WHERE DATED = :TEXT_TOP_DATED AND PRODUCT_ID = :LOV_PNAME;
		:TEXT_TOP_DATED := :TEXT_TOP_DATED + 1;
		END LOOP;
END;