复选框绑定文本框，使文本框变灰

<script type="text/javascript"> 
function changeStatistics(){ 
var val = $("#statistics").val(); 
if(val=="A"){ 
  $("#agents").css("background-color","").removeAttr("disabled"); 
}else{ 
  $("#agents").css("background-color","#F2F2F2").val("").attr("disabled","disabled"); 
} 
} 
$(function(){ 
changeStatistics(); 
}); 
</script> 


<th> 
考勤统计 : 
</th> 
<td> 
<select name="statistics" id="statistics" class="input-txt" style="width: 123px;" onchange="changeStatistics()"> 
<option value="A" ${statistics=='A'?'selected':''}>个人</option> <option value="B" ${statistics=='B'?'selected':''}>职级</option> </select> 
</td> <th> 营 销 员: </th> <td> <input name="agents" id="agents" type="text" class="inputbox" disabled="disabled" value="${agents}" </td>