Setting default value using pl/sql

Question

I am having trouble writing the correct syntax for either a pl/sql expression or function on the default value section for a checkbox item. I share the same form for showing data in edit mode and creating new records. When the instance is a new record, I want an item called P12_ACTIVE to be set to Y (yes).
I have tried several variations like:
begin
select distinct 'Y'
into :P12_ACTIVE
from VMS_PROSPECTING_ITEMS
where order_id != :P12_ORDER_ID;
end;
-OR-
declare defaultvalue varchar2(10);
begin
if not exists (select *
from VMS_PROSPECTING_ITEMS
where order_id = :P12_ORDER_ID) then
defaultvalue := 'Y' ;
end if;
return defaultvalue ;
end;
-OR-
as a pl/sql expression....
select distinct 'Y'
from VMS_PROSPECTING_ITEMS
where order_id != :P12_ORDER_ID;
end;
Dawn

Answer 1

This is my LOV definition for the item:
STATIC: ;Y
If I put Y as the default value, then the check box is always marked, even when the record is one that was edited; therefore potentially changing the active status incorrectly. I would like one of my examples to work right. My second example throws this error:
Error ERR-9131 Error in PLSQL function body for item default code, item=P12_ACTIVE
ORA-06550: line 3, column 8: PLS-00204: function or pseudo-column 'EXISTS' may be used inside a SQL statement only ORA-06550: line 3, column 1: PL/SQL: Statement ignored.