It is possible but you are limited to the same unit of measure on the Y axis. For example it is possible to do something like monthly sales as a bar, with a 3 month moving average sale as a line. I have done this based on a cube using MDX. Sorry, I am do not have the source any longer so I can't look up the details for you. I am too new in my current position to be that far along with my data.
Good luck, sorry I couldn't be of more help.