Arvand, Are you claiming that a Stored Procedure that returns one row of data can be invoked by using the Database Element and selecting "single"? Have you tested this? I'd like to pass this information along to my students if it's true.
Yes, you can run a stored proc in CVP as long as it returns at least one row of data. I have done it many times. All you need to do is to treat the SP as a select query.