Quick Question - Button in _down mode

I have a main menu in my website. Clicking on a mc button takes you to the portfolio section. There is a secondary menu using tab-like mc buttons. I would like to have tab#1 in the down state because that is the active subsection. I have used the code in my actions layer.

workNav1.onEnterFrame = function() {
workNav1.gotoAndStop("_down", 1);
delete this.onEnterFrame;
};

The mc button is depressed as I wanted it to be. But when I click to other tabbed subsections, tab#1 is still depressed as well. I’m not sure if I am using the wrong code (onEnterFrame) where it is or if I need some code to deselect tab#1 when other tabs are selected. If there is code I am missing or need to be corrected. Please let me know. I appreciate any help and advice.

Thank you very much,

T