Web Help Skin Editor

I'm developing a new skin using RoboHelp 7. I added a new button (we'll call it Demos). I have a selected image (demos.gif) and an unselected image (demos_unselected.gif). The Demos page is a link to a page called Demos.htm. When I compile the help system, and the button is displayed on the top navigation, the Demos button does not stay highlighted after the page is opened. Other buttons, such as Contents, Search, Glossary (all standard buttons) stay highlighted after the item is selected. Is there a different way to approach this? Do I have to use a JavaScript call for this instead to make the button stay highlighted? Please advise.