function openwindow (url,wtitle,xsize,ysize,scroll)
{

var x,y, windowsize;
x = Math.round ((screen.width - xsize)/2);
y = Math.round ((screen.height - ysize)/2);

	windowsize = 'left='+x+',top='+y+',width=' + xsize + ', height=' + ysize + ',toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars='+scroll+',resizable=0';
	open_window = window.open(url, wtitle, windowsize );

	if(open_window != null) open_window.focus();
	if(open_window.opener == null ) open_window.opener = window;
}