Determining focus of IWebBrowser2

Hi,

I am writing IE extensions as a COM tool band and a BHO (Browser Helper Object).  I need to determine if the web browser has the focus or not.  I already have access to the IWebBrowser2 interface, so I really just need a simple function like this to return the focused state of the specified web browser:

function WebBrowserFocused(IE: IWebBrowser2): Boolean;

It should return True when the user is within the page and capable of interacting with it, False otherwise (for example when the user is in the address bar or within a tool band).

Could you please provide the code to implement this?

I've looked at the IWebBrowser2 reference below, but I'm still unsure of how to determine the focus:

http://msdn.microsoft.com/library/default.asp?url=/workshop/browser/webbrowser/reference/ifaces/iwebbrowser2/iwebbrowser2.asp

Thanks in Advance,

Richard