Need an alert for Customer Ref. No on Sales order.

Question

Dear All,
I have a question concerning Customer Ref. No. tab in the Sales Order.  We use this tab to enter the customers PO number.  if I create and save a Sales Order with a PO number, is there a way to ALERT me when I try to make a new Sales Order using the identical PO number as previously saved. 
e.g. I have a SO#1 Customer Ref. No is #10. Then I have a SO#5 Customer Ref. No. is #10 too. When I type in #10, is there anyway to pop-up me an ALERT to let me know I have #10 for SO#1 already?
Thanks.
Yuka

Answer 1

Hi Yuka,
Check below code in SP_Tran
If @object_type = '22'
     begin
          Declare @refcli as nvarchar(2)
          Select @refcli =
          (SELECT top 1 T0.NumAtCard
          FROM OPOR T0
          where T0.docentry = @list_of_cols_val_tab_del
          order by NumAtCard
          from OPOR where docentry = @list_of_cols_val_tab_del
          if @refcli='' or @refcli is null Or @refcli=@refcli
          begin
          set @error = 1
          set @error_message = 'No vendor References !!! Or vendor References is Already exists!!!'
     end
end
Hope this will helps you.
Thanks,
Sachin