var delay = 1000
var timerId, flash = true, i = 0, clockDisp, amPm
function clock() {
   if (i <= 500) {
      i++
      var now = new Date()
      var theHour = now.getHours()
      var theMin = now.getMinutes()
      amPm = ((theHour < 12) ? " AM" : " PM")
      theHour = ((theHour >= 12) ? theHour-12 : theHour)
      clockDisp = " " + ((theHour < 10)? " " : "") + theHour
      clockDisp += ((flash) ? ":" : " ")
      clockDisp += ((theMin <10) ? "0" : "")
      clockDisp += theMin + amPm
      document.clock.elements[0].value = clockDisp
      flash = !flash
      timerId = setTimeout("clock()", delay)
   } else { 
      clearTimeout(timerId)
      document.clock.elements[0].value = ""
   }
}