Duplicates should be eliminate in an LOV

Question

Hi,
I have a requirement in that,i created a Multi-Record block in the form.In the Multi-record block,say for a field name "Plot No" i have attached a LOV to display the List of Plot Nos.My requirement is that,If you insert a Plot No in one record through Plot No LOV ,then if you try to insert the Plot No in the next record,the LOV should not display the previous Plot No.How can we implement this.
I have implemented this code in when-validate-item of the particular column.But it does not work.Please help is any modifications has to do.In this code,the fields i mentioned are not primary keys.
DECLARE
     cnt NUMBER;
     rg_name VARCHAR2(40) := 'PLOT_NO_CA';
     rg_col1 VARCHAR2(20) := 'DOC1_ID';
     rg_id RecordGroup;
     gc_id GroupColumn;
     rowcount NUMBER;
     row_value NUMBER;
BEGIN
     SELECT count(*)INTO cnt FROM XX_CIS_CANE_ADVANCE_LINES3 WHERE doc1_id = :CUTTING_ADVANCE.DOC1_ID;
     IF cnt = 0 THEN
     -- create a record group dynamically
     rg_id := Find_Group(rg_name);
     IF Id_Null(rg_id) THEN
          rg_id := Create_Group(rg_name);
          gc_id := Add_Group_Column(rg_id,rg_col1,NUMBER_COLUMN);
     END IF;
     Add_Group_Row( rg_id, END_OF_GROUP );
     rowcount := get_group_row_count(rg_id);
     gc_id := Find_column('PLOT_NO_CA.DOC1_ID');
     set_group_number_cell(gc_id,rowcount,to_number(:system.cursor_value));
FOR i IN 1 .. get_group_row_count(rg_id)-1
LOOP
     row_value := get_group_number_cell(gc_id,i);
     IF row_value = :CUTTING_ADVANCE.DOC1_ID THEN
          fnd_message.set_string('already exists');
          fnd_message.show;
          DELETE_GROUP_ROW(rg_id,rowcount-i);
          RAISE form_trigger_failure;
     END IF;
END LOOP;
ELSE
fnd_message.set_string('Data is already exists in DATABASE');
fnd_message.show;
Raise form_trigger_failure;
END IF;
END;
Thanks&Regards
Sudhakar J

Answer 1

Hi Francois,
If i cleared the Record,the Cleared record is not showing when once again invoke the LOV.How can i modify the code given by you for this scenario.
Please help me.
Thanks&Regards
sudhakar