How to use GO_BLOCK in POST_CHANGE trigger?

Question

Hi All,
I have a post_change trigger on a text item, I wanna change the background color (using visual attribute) of some items in another block according to the value of that text item mentioned.
But when I put a value for the first time some backgrounds are changed and when I change the value the previous actions for backgrounds are still, How to clear the affect of all the previous changes of the value.
I wrote this code on PST-CHANGE trigger on that item:
BEGIN   
    GO_BLOCK('BLOCK1');   
    SET_ITEM_PROPERTY(:SYSTEM.CURSOR_ITEM, VISUAL_ATTRIBUTE,'DISPLAY_ITEMS');
    LOOP
        NEXT_ITEM;
        SET_ITEM_PROPERTY(:SYSTEM.CURSOR_ITEM, VISUAL_ATTRIBUTE,'DISPLAY_ITEMS');
        EXIT WHEN :SYSTEM.CURSOR_ITEM = 'BLOCK1.DATE_QUERY'; -- THIS IS THE LAST ITEM IN THE BLOCK
    END LOOP;
    IF :REP_SID = '01' THEN   
        SET_ITEM_PROPERTY('BLOCK1.SUS', VISUAL_ATTRIBUTE,'PAR_ITEMS');
    ELSIF :REP_SID = '02' THEN
        SET_ITEM_PROPERTY('BLOCK1.NAMEE', VISUAL_ATTRIBUTE,'PAR_ITEMS');
    ELSIF :REP_SID IN ('05','06','07','08','09','10') THEN
        SET_ITEM_PROPERTY('BLOCK1.VIS', VISUAL_ATTRIBUTE,'PAR_ITEMS');
        SET_ITEM_PROPERTY('BLOCK1.AT', VISUAL_ATTRIBUTE,'PAR_ITEMS');
    ELSIF :REP_SID = '20' THEN
        SET_ITEM_PROPERTY('BLOCK1.TOO', VISUAL_ATTRIBUTE,'PAR_ITEMS');
        SET_ITEM_PROPERTY('BLOCK1.DATE_QUERY', VISUAL_ATTRIBUTE,'PAR_ITEMS');
    END IF;
END;
The previous code gives me this error: Illegal restricted procedure GO_BLOCK. How to solve OR Is there another way to achieve the same purpose Plz?
Thank you
Note: I'm using Oracle DB 10G, Forms 6i

Answer 1

use Key-next_item instead of POST_CHANGE.
It will work.
Also SET_ITEM_PROPERTY(:SYSTEM.CURSOR_ITEM, VISUAL_ATTRIBUTE,'DISPLAY_ITEMS'); will not work
You have to use
Set_Item_Instance_Property( SYSTEM.CURSOR_ITEM, SYSTEM.CURSOR_RECORD,
        VISUAL_ATTRIBUTE,'DISPLAY_ITEMS');