list box items moving clientside code

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C#

ASP.NET

I have 10 listboxes in my aspx page. For all 10 listboxes same function is used. For some buttons I want to add listbox data to grid. Can you help me? My javascript code is shown below:

<script language="javascript" type="text/javascript" >
    function MoveItem(ctrlSource, ctrlTarget) {
       var Source = document.getElementById(ctrlSource);
       var Target = document.getElementById(ctrlTarget);

       if ((Source != null) && (Target != null)) {
           while ( Source.options.selectedIndex >= 0 ) {
               var newOption = new Option(); // Create a new instance of ListItem
               newOption.text = Source.options[Source.options.selectedIndex].text;
               newOption.value = Source.options[Source.options.selectedIndex].value;

               Target.options[Target.length] = newOption; //Append the item in Target
               Source.remove(Source.options.selectedIndex);  //Remove the item from Source
           }
       }
}

I tried the above code to move items between listbox using html input button. The problem is that when I am trying to save listbox.items.count is giving 0. Can anyone tell me why this is happening? And also, when post back occurs, the listbox items are lost.