wordpress html

Please your help.
Into a wordpress page, I have a “visual editor”; into it I have the next code:

<form>
   <span>Seleccone el mes:</span>
   <select style="width:120px" id="mesValor" name="mesValor" onchange="myFunction()">
      <option selected="selected" value="">SelectOne</option>
      <option value="01">Enero</option>
      <option value="02">Febrero</option>
   </select>

<script>
   function myFunction(valorCliqueado) {
      var x = document.getElementById("mesValor").value;
      document.getElementById("demo").innerHTML = x;
}
   function myFunction() {
      var x = document.getElementById("mesValor").value;
      document.getElementById("myAnchor").href = "http:\arh\dir11\a.txt";
      document.getElementById("demo").innerHTML = "The link above now goes to www.cnn.com.";
   }

</script>

<p><a href="http:\arh1\a.txt">Acceso</a></p>
</form>

but it is not working.

I need to change

<p><a href="http:\arh\dir1\a.txt">Acceso</a></p>

to

<p><a>01\a.txt">Acceso</a></p>
or
<p><a>02\a.txt">Acceso</a></p>

Thanks for your help