Help please...html frames and sending instructions between them

Please someone help me out here…

I have a page with two html frames, named ‘nav’ and ‘main’. I have a flash menu in the ‘nav’ frame named ‘navigation.swf’. When you click a menu button in this movie, it loads a corresponding page in the ‘main’ html frame, and creates a highlight on that button by going to and stopping on the correct keyframe. For instance, if you click the “contact” button, the ‘contact.htm’ page loads in the ‘main’ html frame, and the “contact” button highlights to reflect the menu choice and stays that way until you click a different button.

Only problem is when you click a link in the ‘main’ html frame, the button highlight doesn’t know to change.

How can I make it so that when you click a link in the ‘main’ frame (thus loading a new page) the ‘navigation.swf’ in the ‘nav’ html frame knows to change keyframes to make the menu button highlight correctly?

Thanks much in advance…