Como puedo pasar un valor de javascritp a un textbox en asp.net..?..tengo este codigo:
 
<form name="Tick">
<input type="text" size="11" name="Clock"> 
</form>
<script>
<!--
    /*By George Chiang (JK's JavaScript tutorial) 
http://javascriptkit.com
    Credit must stay intact for use*/
    function show() {
        var Digital = new Date()
        var hours = Digital.getHours()
        var minutes = Digital.getMinutes()
        var seconds = Digital.getSeconds()
        var dn = "AM"
        if (hours > 12) {
            dn = "PM"
            hours = hours - 12
        }
        if (hours == 0)
            hours = 12
        if (minutes <= 9)
            minutes = "0" + minutes
        if (seconds <= 9)
            seconds = "0" + seconds
        document.Tick.Clock.value = hours + ":" + minutes + ":"
+ seconds + " " + dn
        setTimeout("show()", 1000)
    }
    show()
//-->
</script>  
Saludos..!!