[рони]

jack8888,

<script>
      var VAL556 = "20/1";
      function Inc20ut(obj)
      {
         VAL556 = {1 : "20/1",2: "38/1", 3 : "15/1"}[obj.value]
         alert(VAL556)
      }
  </script>
<select size="1" name="select1" id="select1" onchange="Inc20ut(this)" >
<option selected value="1">SEL1</option>
<option value="2">SEL2</option>
<option value="3">SEL3</option>
</select>