Airport express with external HD?

I have a macbook and a home network and have been looking to add an airport express to have airtunes. I know you can use the airport express to hook up a "wireless" printer so I can print over the network, is it possible to hook up an external HD to the airport express and access it over the network?
I already have a wireless router (or whatever its called) that I got from the cable company when I started my internet service so I don't want to have to replace it with an airport extreme base-station, at least not yet.

Thanks!

Thanks...

Cool, thanks. I did not find it anywhere specific so I figured I would get a solid answer.