.net combobox

I am making a web browser in vb2012 and for the url part i am using combobox . I am facing problem when i have to use forward button and back button. It changes the web page in web browser control but does not have any change in  combobox for the url part. It keeps the same that have entered when the page loads. What should i do to make the url part works?
Plz suggest something. Its urgent!!