var new_window
function open_window(url,width,height){		 
    	if (!window_available()) {
     		new_window = window.open(url, "", "width="+width+",height="+height);
   			}
   			else {
    		new_window.focus();
   			}
   		
}
		
function window_available() {
    if (!new_window) {
        return false;
    }
    else if (new_window.closed) {
        return false;
    }
    else {
        return true;
    }
}