Navigating URL in a particular tab

Hi,

I am developing an extension in javascript. I want to block certain
web pages, after navigation is completed. I have implemented
nsIWebProgressListener, and I am checking the URL when I receive
STATE_STOP, here if I get the blocked site, I want to replace it with
my custom page.

The problem occurs when multiple tabs are opened and when I use
loadURI of nsIWebNavigation, it loads page in currently selected tab.

So my question is that how can we load a page in a particular tab?

Please help me out. I am stuck here.

Thank you.