Internal link - Navigation bar state

Hi,

I've set up a site using a frameset. The navigation bar sits in the left frame
and the body of the site in the mainFrame. When you click on links on the nav
bar - only the mainFrame changes. I have some internal links in the mainFrames
linking to other pages as listed on the navbar. However, when you click on an
internal link and change page, the navbar does not move to the down state of
the page you are now on. Can anyone help and advise how to get the navbar to
change to the down state of current page when activated by an internal link on
another page.

Thanks muchly!