Where to write the code for mail in master page

below is my code. please anyone tell me where to write vbscript to send email after validating the fields


<%@ Page Language="VB" MasterPageFile="~/Master.master" AutoEventWireup="false" CodeFile="Enquiry.aspx.vb" Inherits="Enquiry" title="Enquiry - MTM Active" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ConPage" Runat="Server">
<script type="text/javascript" src="Js/Blank.js"></script>
<script type ="text/javascript">

function CmdSubmit_onclick()
{
if (fnValidate()==true)
return true;
else
return false;
}

function fnValidate() {
if(IsBlank(" Name",document.getElementById ("TxtName").value)==false)
        {
            document.getEle ...