how to use gpg with a smartcard, when there is no smartcard

[Stephan Hermann]

Hi,

I have a little problem with gnupg and smartcards.
I added to my key a signing subkey for my smartcard. This works great 
when the smartcard reader is attached to my computer, which is my home 
workstation.

Now I have a copy of my secret key etc. on my usb stick and want to use 
my key for signing at work, without having a smartcard reader attached.

Gnupg complains now, that it can't find the smartcard reader, which is 
true at work, and I'm not able to use any signature function anymore.

Is there a way to tell gnupg, to use another subkey or whatever it 
needs, for signing?

There must be a possibility to sign something without having a smartcard 
reader attached, right?

Thx for your help and the great software,

\sh