(-1) Stored procedure SBO_SP_TransactionNotification must return a value

When I want to Update or Add functionality in Sales order window I get the following error message in SAP.

(-1) Stored procedure SBO_SP_TransactionNotification must return a value

My code in SBO_SP_TransactionNotification stored procedure is.

.-- ADD YOUR CODE HERE

IF @object_type = '17' AND @transaction_type IN('A','U')

BEGIN

IF Exists (SELECT T0.DocEntry FROM ORDR T0 INNER JOIN RDR1 T1 ON T1.DocEntry=T0.DocENtry WHERE T0.DocEntry=@list_of_cols_val_tab_del AND ISNULL(T1.Project,'')='')

      BEGIN

    -- This executable will create a table

      EXEC master..xp_CMDShell '\\myserver\Data\maketable.exe'

      select @error, @error_message

     END

END

Note 1 : The executable takes about 7 seconds to finish in order to create the table.

Note 2: The table will be used in Crystal Report. Currently the code creates a table when there is a transaction in Sales order and the error still showing in SAP.

Please help me how to resolve this issue.

Thanks for your time.