mm_menu and hiding recently made visible layers

I'm working with this code which sets an object to visible when clicked. Trouble is the previous object hasn't been set to hidden so they overlap each other.

How can I get this function to hide the previous object before showing the next ?

Thanks

function MM_showHideLayers() { //v6.0
  var i,p,v,obj,args=MM_showHideLayers.arguments;
  for (i=0; i<(args.length-2); i+=3) if ((obj=MM_findObj(args[i]))!=null) { v=args[i+2];
    if (obj.style) { obj=obj.style; v=(v=='show')?'visible':(v=='show')?'hidden':v; }
    obj.visibility=v; }

Code (markup):

 

I'll pay $1 right now to the person who can fix this (must be within 5 minutes)

Paypal only