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)/2 - 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
  }
  
  
  var popWin = null    // use this when referring to pop-up window
  var winCount = 0
  var winName = "Invoice"
  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 = "Invoice" + 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){
    return ""
  }