Airport and Timecapsule working together
Hello
YES YOU CAN:
The Airport Express (802.1n) can be configured as a client of the Timecapsule.
Apple's step by step guide is here:
http://support.apple.com/kb/HT1731
Using AirPort Setup Assistant
Plug AirPort Express into a power outlet.
On your computer, join the wireless network created by AirPort Express.
Open AirPort Setup Assistant. Mac users: Find it in /Applications/Utilities/. Windows users: On the Start menu, point to All Programs and click AirPort.
When you see the Introduction screen, click Continue.
Select "Set up a new AirPort Base Station" and click Next.
When the AirPort Setup Assistant confirms that it has found your AirPort Express, click Continue. (If your AirPort Express wasn't found, click Try Again.)
Select "Connect to my current wireless network."
Be sure that "Extend the range of my AirPort wireless network" is not selected (this option is used only for WDS).
Click Next; AirPort Express Assistant will scan for your existing wireless network. Once it finds it, click Next again.
Choose the correct network (there may only be one) from the Wireless Network Name menu. If the wireless network is password protected, you will be prompted to enter the password. Enter the password and then click Next to continue.
Note: If you have difficulty with your password, you can get help with joining a third-party WEP-protected network.
Enter the name of your AirPort Express.
Tip: If you don't know the name, it's what appears in iTunes as the name of your AirTunes remote speakers.
Click Next.
Assign an administrator password for AirPort Express. This password can be different from any network password, and is used for just changing settings on AirPort Express.
The Summary screen outlines the configuration options you've set. Optionally, you can click Show Passwords to review the administrator and network passwords. Finally, click Next to update AirPort Express with your settings.