Access java script local variable in C#

Question

Hello Everybody,

Friends I have problem  in using local variable of java script in the java script function.

I am using code

<script language="javascript" type="text/javascript">

function CharacterCount() {

var txtMessage = document.getElementById('<%= txtMessage.ClientID %>'); 

    var numberOfChars = txtMessage.value.length;

   <%= this.txtchracters.Text = numberOfChars%>

}

But it is not accessing the local variable of java script function "numberOfChars" while assigning to this.txtchracters.Text

Please suggest me some technique to overcome this problem. 

Thanks