// Copyright 1999 - 2002 by Ray Stott, Pop-up Windows Script ver 2.0
// OK to use if this copyright is included
// Script is available at http://www.crays.com/jsc          

// abridged by Martin Waugh

var popWin = null    // use this when referring to pop-up window
var winCount = 0
var winName = "popWin"

function openPopWin(winURL, winWidth, winHeight, winFeatures, winLeft, winTop)
{
	var d_winLeft = 20  // default, pixels from screen left to window left
	var d_winTop = 20   // default, pixels from screen top to window top

	winName = "popWin" + winCount++ //unique name for each pop-up window
	closePopWin()           // close any previously opened pop-up window
	
	if (openPopWin.arguments.length >= 4)  // any additional features? 
		winFeatures = "," + winFeatures
	else 
		winFeatures = "" 
		
	if (openPopWin.arguments.length == 6)  // location specified
		winFeatures += getLocation(winWidth, winHeight, winLeft, winTop)
	else
		winFeatures += getLocation(winWidth, winHeight, d_winLeft, d_winTop)
		
	popWin = window.open(winURL, winName, "width=" + winWidth 
	       + ",height=" + winHeight + winFeatures)
	}
	
function closePopWin()
{    // close pop-up window if it is open 
	if (navigator.appName != "Microsoft Internet Explorer" 
		|| parseInt(navigator.appVersion) >=4) //do not close if early IE
		
	if(popWin != null) if(!popWin.closed) popWin.close() 
}

function getLocation(winWidth, winHeight, winLeft, winTop)
{
	var winLocation = ""
	
	if (winLeft < 0)
		winLeft = screen.width - winWidth + winLeft
	if (winTop < 0)
		winTop = screen.height - winHeight + winTop
	if (winTop == "cen")
		winTop = (screen.height - winHeight)/3 - 20
	if (winLeft == "cen")
		winLeft = (screen.width - winWidth)/2
	if (winLeft>0 & winTop>0)
		winLocation =  ",screenX=" + winLeft + ",left=" + winLeft	
	                     + ",screenY=" + winTop  + ",top="  + winTop
	else
		winLocation = ""
		
	return winLocation
}
<!--END Pop-up Windows Script-->