Obtain Credentials On-Demand

[petesea@bigfoot.com]

Using the Kerberos (1.6.2) and OpenSSH (4.7p1) available with Mac Leopard 
(10.5)... is there a way to get the Kerberos GUI-based "Authenticate to 
Kerberos" dialog to be displayed automatically if there are no credentials 
or the credentials have expired?

In other words, if I go to a command line and run:

   $ ssh bozo at zippy.com

and there are no credentials or the credentials have expired, I'd like to 
see the "Authenticate to Kerberos" dialog popup automatically.