Moviclip control (if statements)

Hey guys,

So basically I’m building a site. When you click one of the menu items it
loads the page using the ‘with’ command.

Example:

About button

with(_root.about){
play();
}

So when you click a button it makes the movieclip play,
then when you click the button again or the close button
the movieclip plays again and it dissapears.

What I am looking for is when you click a different button
if on of the other pages is open it closes then the new one opens
so you dont get the overlapping pages.

I think I need if else statements but have no idea of how to go about it.

My fla file is attached.

Thanks in advance.