Is it possible to write a class that extends a custom VF controller, and then use the new class as the controller for a page?  Can I extend a class that is itself an extension of a standard controller, as opposed to a fully-custom controller?

It's the latter that I'm trying to do right now.

I tried creating an extension.  I added the "virtual" keyword to my existing controller, then defined a new child class something like so:

public class CTRL_CustomWizard extends CTRL_FooWizard {

 Does this mean I can't do it, or do I need to do something else?  The constructor in the parent class can't have no arguments, because it's an extension of a standard controller, so the constructor is defined like:

public CTRL_FooWizard (ApexPages.StandardController controller) {

Thanks much!