Forms :: Update Field Based On Another Field Checkbox

I have a table where i need to update one field values based on another field of the same table , simply as it is.I have done this using one select all check box , on clicking that all check boxes of item_trans table will get selected , then i will un select some of check box and then using one button, i will update the value of the fields which are checked only.

I have put the sample code but when i am updating its taking long time and hanging.I am also attaching the form based on the test case provided.

--tables with insert statement
create table item_trans (trans_item varchar2(12),trans_qty number,trans_act_qty number)

insert into item_trans(TRANS_ITEM,TRANS_QTY,TRANS_ACT_QTY) VALUES ('TREE1',40,NULL);
insert into item_trans(TRANS_ITEM,TRANS_QTY,TRANS_ACT_QTY) VALUES ('TREE2',20,NULL);
insert into item_trans(TRANS_ITEM,TRANS_QTY,TRANS_ACT_QTY) VALUES ('TREE3',20,NULL);

--i want to set the value of trans_Act_qty as trans_qty

--i create one dummy or test block to keep the select all check box. for that table test script is

CREATE TABLE TEST
(
C VARCHAR2(2000 BYTE),
B NUMBER,
A NUMBER
);

insert into test (C,B,A) values ('A',1,1);

--code written in select all check box which is created on test.block.

BEGIN
GO_BLOCK('item_trans');
FIRST_RECORD;
LOOP
:M_END_YN := :M_END_ALL;
[code].......

--code written in M_END_YN ( actual check boxes where i will uncheck).

IF :M_END_YN = 'N' THEN
:M_END_ALL := 'N';
END IF;

--code written on button to update those values which are checked.

BEGIN
GO_BLOCK('item_trans');
FIRST_RECORD;
LOOP
IF :M_END_YN = 'Y' THEN
[code]......