hi Dean,
the normal way to pass multiple values to a stored proc is using the subeport method that you've already used. however it doesn't really work for the main report as you've seen. a couple of options
1) use another subreport to display the data that you want in the main report
2) write out your stored proc logic (if possible) as a query in a Command object...is there a particular reason that a stored procedure is being used?...i.e. are you using something that requires hana sql script, or create update delete actions?
-jamie