Time Capusle extending wireless

[xion]

Allright,

I recently bought myself a time capsule for my dorm, but my exams are over now and i'll be home for about a month so I took the time capsule home (most of my movies are on it )

Now i wanted to "extend" my current wireless (airport express), but my time capsule won't show up in my airport utility? (isn't connected to any internet cable)

My current internet looks like this:
Internet -> modem -> router -> PC
                                    -> PC
                                       -> Airport express -> MBP's

Do i have to connect the airport express to my timecapsule with a cable or can it be done wirelessly so i can put the timecapsule in my room?

(Will draw the internet connection to explain this better)

Much appreciated.

 

[xion]

Basicly this is what my setup looks like (left out the pc's cuz they are not wireless but connected directly to the router)

What i want is that the airport express (blue) sends a wireless signal to my timecapsule (red) so it will extend my wireless.

Is this possible?