asterisk users - Nov 2004 - Hookflash with cisco 827-4v

Hi, 

I have setup my cisco 827-4v to handle incoming and outgoing calls
with asterisk with an isdn line.
My problem is that I can't use features like call forwarding or
holding because the router doesn't support the hookflash key.

Is there anyone that has succeded in using the hookflash with the FXS ports?

Is there a way to simulate the hookflash with other keys combinations?

Thanks.
Davide Malagoli