Hidden Dropdown

The selection of the first dropdown determines which second dropdown populates

HTML

<table style="border:2px solid #006633" bgcolor="#CCBFA3"; id="my_table">
    <tr>
      <td>
        <input type="checkbox" name="ord_31" id="orderId_31" value="true" /> Furosemide (Lasix) 40 milligram   
          <select name="cprompt_31_1" id="cprompt_31_1">
            <option value="ORAL">orally</option>
            <option value="IV">intravenously</option>
          </select> 
          <select name="cprompt_31_2" id="cprompt_31_2">
            <option value="Q12H">Q12H</option>
            <option value="QDAY">QDAY</option>
            <option value="Q6H">Q6H</option>
            <option value="Q8H">Q8H</option>
            <option value="BID">BID</option>
          </select>
          <select name="cprompt_31_3" id="cprompt_31_3" class="hide">
            <option value="ONCE">ONCE</option>
          </select>
      </td>
    </tr>
  </table>

CSS

body{
 background-color:#D1D1D1;  
 font-size: 62.5%; 
 margin: 30px;
}
td{
 text-align:left;
 font-family: Tahoma, Verdana, sans serif;
 font-size: 10pt;
 vertical-align:top;
}
td.checked { background: yellow; }
select.hide{ display:none; }

JavaScript

// Lasix Frequency Selection

$(function() {
    $("select#cprompt_31_1").change(function() {
        if ($('select#cprompt_31_1 option:selected').val() == "ORAL") {
           
            $("select#cprompt_31_2").removeClass("hide");
            $("select#cprompt_31_3").addClass("hide");
        } else {
            $("select#cprompt_31_2").addClass("hide");
            $("select#cprompt_31_3").removeClass("hide");
        }
    });
});

$("input:checkbox").click(function() { $(this).parent("td").toggleClass("checked");
});