Add ListBoxItem to ListBox from C# code behind using a javascript function

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C#

ASP.NET

Javascript

HTML

ListBox

I have a page that's written using ASP.Net (C#)
I have a button that is NOT a server control but is just an anchor (

<a href="java<!-- no -->script:Add_Button_Click">Add</a>

).
The menu code looks like this:

<ul>
<li><a href="java<!-- no -->script:Add_Button_Click('someString');">Add Value To ASP.Net ListBox</a></li>
</ul>

The "Add_Button_Click" (JavaScript):

<script type="text/javascript">
function Add_Button_Click(someStringValue) {

}
</script>

The "Add_Button_Click" (C# Code Behind):

public static void Add_Button_Click(string someValue)
{
    ListBox box = Page.FindControl("ListBox1") as ListBox;//I'm not too sure if this part works but it's what I have so far.
}

In my page's Code Behind I need to be able to do two things:
1.) Call a C# function from the JavaScript code.
2.) In the C# function that's being called from JavaScript I need to add a ListBoxItem to an ASP.Net ListBox Server Control that resides on my page.

I've searched the web but can't seem to find a way to make any of these things work correctly.

Please show/tell me with example code how you guys would go about doing this, Thanks!!!