EDIT: I haven’t tried this, so I can’t vouch for it! And you already know you shouldn’t be doing this, so please don’t do it. BUT…
Try looking here: http://sqlblog.com/blogs/denis_gobo/archive/2008/05/08/6703.aspx
The key bit is this bit which I have attempted to tweak for your purposes:
DECLARE @SQL varchar(500)
SELECT @SQL = 'osql -S' +@@servername +' -E -q "exec dbName..sprocName "'
EXEC master..xp_cmdshell @SQL