Forms :: Insert Values In A Table Through Ref

Table Structure:
Name of Table: info
Column: ID, Name, Cell,Cell1,Ref

i want to insert these values in a table through ref (key next item).
-----------------------------------------------------------
Key next Item Triger
DECLARE
A NUMBER;
B NUMBER;
BEGIN
SELECT :CELL,:CELL1 INTO A,B FROM DUAL;
[code].......
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but when i press enter(ref Key_next_item) it will return error:

FRM-40735: KEY_NEXT_ITEM RAISED UNHANLEDED EXCEPTION ERROR: ORA 40102