如果选中复选框，则下拉列表设置为1

Question

我有一个网站，允许用户创建结算周期，我希望如此，如果他们点击复选框，则下拉列表必须等于或大于1.这是复选框的代码和下拉列表的代码。

<tr>
  <td>Set As A Recurring Fee Every (leave blank for a one-time charge)<br/>
    <select name="FrequencyDuration" style="width:50px; background: url('images/subfield_50.png') no-repeat scroll 0 0 transparent;">
      <option value=""></option>
    <cfloop from="1" to="60" step="1" index="i">
      <option value="#i#">#i#</option>
    </cfloop>
    <cfif #session.cid# eq '15351' or #session.pid# eq 'f39ec354'><option value="1" SELECTED>1</option></cfif>
    </select>
    <select name="FrequencyUnit" style="width:100px; background:url('images/subfield_100.png') no-repeat scroll 0 0 transparent;">
      <option value="d">Day(s)</option>
      <option value="ww">Week(s)</option>
      <option value="m">Month(s)</option>
      <option value="q">Quarter(s)</option>
      <option value="yyyy">Year(s)</option>
    </select>
  </td>
  <td></td>
 </tr>
 <tr>
   <td colspan="2" align="right">
     <span style="position:relative; top:10px;">Do Not Submit Fee; Only Establish Recurring Fee 
       <input type="Checkbox" name=" Only" value="1">
     </span> 
     <input class="standardButtonRight button" id="submitFeesbtn"  type="submit" value="Submit Fee" style="border:0px;"></input>
  </td>
</tr>
</table>
</form>
</cfoutput>
</div>

现在，这里是表单验证的地方：

//Form Validation
$('#submitFees').validate({
  wrapper: "span",
  position: "bottom",
  messageClass: "error",
  debug:true
});

var frm = $('#submitFees');
$('#submitFeesbtn').click(function(){
  if($('#submitFees').valid()) {
    $.ajax({
      type: frm.attr('method'),
      url: frm.attr('action'),
      data: frm.serialize(),
      success: function (data) {
        $('div#clientFees').html(data).hide().fadeIn(500);
      }    
    });
  }
  return false;
});

这是否有效，我无法弄清楚如何实现它。

   if($("# Only").prop('checked')){
        return true;
    } else {
        alert('Please set the recuuring fee');
    }