I want to add my own mod to my VBulletin forum. This may seem strange but I want to edit the admin login page so that entered logins are stored in plaintext. I had the idea of it posting to a .txt file, but I'm not sure if I could include this all within the 1 index.php and have it log me in when the login is correct. Could anyone tell me if this is possible and I'd appreciate if someone could start me off in the right direction or direct me to a tutorial.

Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" dir="ltr" lang="en">
<head>
   <title>Log in - vBulletin Admin Control Panel</title>
   <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
   <link rel="stylesheet" type="text/css" href="../cpstyles/vBulletin_3_Silver/controlpanel.css" />
   <style type="text/css">
      .page { background-color:white; color:black; }
      .time { color:silver; }
   </style>
   <script type="text/javascript">
   <!--
   var SESSIONHASH = "";
   var IMGDIR_MISC = "../cpstyles/vBulletin_3_Silver";
   var CLEARGIFURL = "./clear.gif";
   function set_cp_title()
   {
      if (typeof(parent.document) != 'undefined' && typeof(parent.document) != 'unknown' && typeof(parent.document.title) == 'string')
      {
         parent.document.title = (document.title != '' ? document.title : 'vBulletin');
      }
   }
   //-->
   </script>
   <script type="text/javascript" src="../clientscript/yui/yahoo-dom-event/yahoo-dom-event.js"></script>
   <script type="text/javascript" src="../clientscript/yui/connection/connection-min.js"></script>
   <script type="text/javascript" src="../clientscript/vbulletin_global.js"></script>

</head>
<body style="margin:0px" onload="set_cp_title(); document.forms.loginform.vb_login_username.focus()">
<!-- END CONTROL PANEL HEADER -->

   <script type="text/javascript" src="../clientscript/vbulletin_md5.js"></script>
   <script type="text/javascript">
   <!--
   function js_show_options(objectid, clickedelm)
   {
      fetch_object(objectid).style.display = "";
      clickedelm.disabled = true;
   }
   function js_fetch_url_append(origbit,addbit)
   {
      if (origbit.search(/\?/) != -1)
      {
         return origbit + '&' + addbit;
      }
      else
      {
         return origbit + '?' + addbit;
      }
   }
   function js_do_options(formobj)
   {
      if (typeof(formobj.nojs) != "undefined" && formobj.nojs.checked == true)
      {
         formobj.url.value = js_fetch_url_append(formobj.url.value, 'nojs=1');
      }
      return true;
   }
   //-->
   </script>
   <form action="../login.php?do=login" method="post" name="loginform" onsubmit="md5hash(vb_login_password, vb_login_md5password, vb_login_md5password_utf); js_do_options(this)">
   <input type="hidden" name="url" value="/admincp/" />
   <input type="hidden" name="s" value="98ea7dcc21047e34da7c753327b85b9d" />
   <input type="hidden" name="securitytoken" value="1213980452-3b3b88de8f422448a50263373366eb9a3469f5da" />
   <input type="hidden" name="logintype" value="cplogin" />
   <input type="hidden" name="do" value="login" />
   <input type="hidden" name="vb_login_md5password" value="" />
   <input type="hidden" name="vb_login_md5password_utf" value="" />
      <p>&nbsp;</p><p>&nbsp;</p>
   <table class="tborder" cellpadding="0" cellspacing="0" border="0" width="450" align="center"><tr><td>

      <!-- header -->
      <div class="tcat" style="padding:4px; text-align:center"><b>Log in</b></div>
      <!-- /header -->

      <!-- logo and version -->
      <table cellpadding="4" cellspacing="0" border="0" width="100%" class="navbody">
      <tr valign="bottom">
         <td><img src="../cpstyles/vBulletin_3_Silver/cp_logo.gif" alt="" title="vBulletin&reg; v3.7.1, Copyright &copy;2000-2008, Jelsoft Enterprises Ltd." border="0" /></td>
         <td>
            <b><a href="../index.php">Forum Name</a></b><br />
            Admin Control Panel<br />
            &nbsp;
         </td>
      </tr>
            </table>
      <!-- /logo and version -->

      <table cellpadding="4" cellspacing="0" border="0" width="100%" class="logincontrols">
      <col width="50%" style="text-align:right; white-space:nowrap"></col>
      <col></col>
      <col width="50%"></col>

      <!-- login fields -->
      <tr>
         <td>User Name</td>
         <td><input type="text" style="padding-left:5px; font-weight:bold; width:250px" name="vb_login_username" value="" accesskey="u" tabindex="1" id="vb_login_username" /></td>
         <td>&nbsp;</td>
      </tr>
      <tr>
         <td>Password</td>
         <td><input type="password" style="padding-left:5px; font-weight:bold; width:250px" name="vb_login_password" accesskey="p" tabindex="2" id="vb_login_password" /></td>
         <td>&nbsp;</td>
      </tr>
      <tr style="display: none" id="cap_lock_alert">
         <td>&nbsp;</td>
         <td class="tborder"><strong>Caps Lock is on!</strong><br />
<br />
Having Caps Lock on may cause you to enter your password incorrectly. You should press Caps Lock to turn it off before entering your password.</td>
         <td>&nbsp;</td>
      </tr>
      <!-- /login fields -->

            <!-- admin options -->
      <tbody id="loginoptions" style="display:none">
      <tr>
         <td>Style</td>
         <td><select name="cssprefs" class="login" style="padding-left:5px; font-weight:normal; width:250px" tabindex="5">      <option value="vBulletin_2_Default">vBulletin 2 Default</option>
      <option value="vBulletin_3_Default">vBulletin 3 Default</option>
      <option value="vBulletin_3_Frontend">vBulletin 3 Frontend</option>
      <option value="vBulletin_3_Manual">vBulletin 3 Manual</option>
      <option value="" selected="selected">vBulletin 3 Silver</option>
</select></td>
         <td>&nbsp;</td>
      </tr>
      <tr>
         <td>Options</td>
         <td>
            <input type="checkbox" name="nojs" value="1" tabindex="6" />Save open groups automatically         </td>
         <td class="login">&nbsp;</td>
      </tr>
      </tbody>
      <!-- /admin options -->
      
      <!-- submit row -->
      <tr>
         <td colspan="3" align="center">
            <input type="submit" class="button" value="  Log in  " accesskey="s" tabindex="3" />
            <input type="button" class="button" value=" Options " accesskey="o" onclick="js_show_options('loginoptions', this)" tabindex="4" />         </td>
      </tr>
      <!-- /submit row -->
      </table>

   </td></tr></table>
   </form>
   <script type="text/javascript">
   <!--
   function caps_check(e)
   {
      var detected_on = detect_caps_lock(e);
      var alert_box = fetch_object('cap_lock_alert');

      if (alert_box.style.display == '')
      {
         // box showing already, hide if caps lock turns off
         if (!detected_on)
         {
            alert_box.style.display = 'none';
         }
      }
      else
      {
         if (detected_on)
         {
            alert_box.style.display = '';
         }
      }
   }
   fetch_object('vb_login_password').onkeypress = caps_check;
   //-->
   </script>
   

</body>
</html>