This article may answer your question.
http://chooseyourstory.com/help/articles/article.aspx?ArticleId=4123
I won't outright say that it's not allowed, but it really depends on what exactly you have in mind. Someone else may be able to better answer your question, but I feel reading that article is a good place to start.
Edit: Mizal was faster with the link, and had more to say than I did. Safe to say the article should be helpful at least. Best of luck. :)