function DoPagingOnEnter()  
    {           
        var ControlPrefix = $get('<%
=hdnListViewClientID.ClientID%>').value;
        if(!
(event.keyCode==48||event.keyCode==49||event.keyCode==50||ev
ent.keyCode==51||event.keyCode==52||event.keyCode==53||event
.keyCode==54||event.keyCode==55||event.keyCode==56||event.ke
yCode==57||event.keyCode==8||event.keyCode == 13))
        {
            event.returnValue=false;
        }
        else
        {  
            var number = 0;		                   
            var Message;
            var PrefixId = $get('<%=hdnNodeID.ClientID%
>').value; 
            number = $get(ControlPrefix+'txtPage').value;
            if(!isNaN(number))
            {
                if (event.keyCode == 13) 
                {
                    var status ='1';
                    var PageFilter = /^[0-9]+$/;
                    if(!PageFilter.test($get
(ControlPrefix+'txtPage').value))
                    {
                        status='0';    
                    }
                    else
                    {
                        number = parseInt(number);
                        var MaxPage = 0;
                        MaxPage = parseInt($get('<%
=hdnMaxPage.ClientID%>').value);                    
                        if(1 > number)
                        { 
                            status ='0'; 
                        }                             
                        else if(number > MaxPage)
                        {
                            status ='0'; 
                        }
                        else 
                        {
                            status ='1';
                        }
                    }                    
                    if(status == "0")
                    {                        
                        var mes = "<%
=CommonMessages.InvalidPage%>";
                        ShowMessage(mes,"<%
=CommonMessages.ErrorHeader%>",'Error');
                        content_resize(); 
                        return false; 
                    }
                    else
                    {
                        __doPostBack
((PrefixId+'$btnPaging'), '');
                    }
                }




   <asp:Button ID="btnPaging" runat="server" Text="Button" 
Style="height: 26px; display: none"
                OnClick="btnPaging_Click" />

then the click event in code behind