Append Value To Url In IE Using Window Handle?

I'm trying to manipulate a URL in an already opened IE browser window. In a nutshell, I need to change "http://www.excelforum.com" to "http://www.excelforum.com/this-is-the-new-part"

The code prior to this does the following:
- Opens a new instance of IE
- Enters the username and password required to get into the site
- Scrapes the source code, imports it into Excel, and parses the data
- Finds a row based on the current date and some text
- Extracts from that row a unique identifier...
- Obtains the window handle ID for the instance of IE displaying the website

Now I need to add the unique identifier to the url. I cannot open it in a new tab or instance of the browser, as it revokes back to the login screen. I was assuming that the best way to do this would be to get the window handle, then just send a "tab" to get back to the URL, and enter the new URL. If there's any other way to do this, I'm all ears. Otherwise, how can I send the keys using the window handle?