var popup_window;
function OpenPopUp(DocumentName, Width, Height)
{
	var window_width = Width;
	var window_height = Height;
	var window_left = (screen.width - window_width)/2;
 	var window_top = (screen.height - window_height)/2 - 20;

	if (popup_window && !popup_window.closed)
		popup_window.focus();

	popup_window = window.open(DocumentName, null,
	"top=" + window_top + ",left=" + window_left + ",width=" + window_width + ",height=" + window_height + ",resizable=no,scrollbars=no,status=no,toolbar=no,menubar=no,location=no,directories=no");
}