How to use a GnuPG card on multiple computers?

[Urs Hunkeler]

Hi,

How can I use a GnuPG card on multiple computers?

My understanding is that when I let the card generate the keys, a stub 
for each key pair is automatically added to my keyring and instructs gpg 
to use the card to encrypt my messages. How can I add such stubs to my 
keyring on a different computer to point to existing keys on my card 
without having to regenerate the keys (which would render the card 
unusable for the first computer)?

Thanks,
Urs