How to add a countdown script to a existing javascript clock?

So I have this code that someone else wrote and I have cron jobs setup to execute every 10 minutes.

What I would lke to display is another timer counting down from the 10 minute mark below it.

Example:
10:14:22PM <~ Current script
05:38 seconds until next event <~ I would like to add this

//clock() recieves server time in php: 
//javascript:clock(".date('G,i,s').") (24-hour format, Minutes, Seconds)

var hours;
var minutes;
var seconds;
var timer=null;
var timed=null;
function clock(hour,minute,second){
  hours=hour;
  minutes=minute;
  seconds=second;
  if(timer){clearInterval(timer);timer=null;}
  timer=setInterval("work();",1000);
}

function addZero(_v)
{
  if(_v<10)_v="0"+_v;
  return _v;
}

function work(){
  if (!document.layers && !document.all && !document.getElementById) return;
  var runTime = new Date();
  var nd = "AM";
  var shours = hours;
  var sminutes = minutes;
  var sseconds = seconds;
  if (shours >= 12) {
    nd = "PM";
    shours-=12;
  }
  if (!shours) shours = 12;
  sminutes=addZero(sminutes);
  sseconds=addZero(sseconds);
  shours  =addZero(shours  );
  movingtime = ""+ shours + ":" + sminutes +":"+sseconds+"" + nd;
  if (document.getElementById) {
    document.getElementById("jsClock").innerHTML=movingtime;
  }
  else if (document.layers)
  {
    document.layers.clock.document.open();
    document.layers.clock.document.write(movingtime);
    document.layers.clock.document.close();
  }
  else if (document.all) {
    clock.innerHTML = movingtime;
  }
  if(++seconds>59) {
    seconds=0;
    if(++minutes>59)
    {
      minutes=0;
      if(++hours>23)
      {
        hours=0;
      }
    }
  }
}

Code (markup):

Any help would be appreciated

 

Is this what you are looking for:

http://choufouni.com/webmaster_tools/stop_watch/

Please PM let me know if there is anything I can do for you.

Have a great day

 

Take a look here

 

wow, thank you both for your help!