I want to add timer countdown on my web page .........

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custom-controls

i want to add a countdown timer on web page and at runtime put my database's field value in it like i have a table Start_time and End_time in db and at code i want to display a countdown if that page open between start date and end date and time shows the left time and decrease by the time dynamically.......... please suggest me how can i do it.
i tried it by the script available at dynamiccode link is http://www.dynamicdrive.com/dynamicindex6/dhtmlcount.htm[^] but i was not succeded to place my data on that script........
var christmas=new cdtime("countdowncontainer2",document.getElementById("<%=lblFullDateTime.ClientID%>").value.ToString())
but it doesn't work for me so help me please......