var statusCheck = null;
function open_window(url) {
   if (statusCheck == null) {
      mywin = open(url,"mywin",'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=0,	 width=600,height=580,left=20,top=20,screeny=20,screenx=20');
      statusCheck = 1;
   }
   else {
         mywin.close();
         mywin = open(url,"mywin",'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=0,width=600,height=580,left=20,top=20,screeny=20,screenx=20');
         statusCheck = 1;
   }
}