<script language = "JavaScript">
function jisuan()
{
var tempjg=0;
tempjg = n1.checked?jiage1.innerHTML*num1.value:0;
tempjg = n2.checked?tempjg+jiage2.innerHTML*num2.value:tempjg;
jieguo.value=tempjg;
}
</script>
<table>
  <tr>
    <td>(价格)</td>
    <td>数量</td>
    <td>选择</td>
  </tr>
  <tr>
    <td id=jiage1>3.6</td>
    <td><input type=text value="0" name=num1 onkeyup="jisuan();"></td>
    <td><input type="checkbox" name=n1 onclick="jisuan();"></td>
  </tr>
  <tr>
    <td id=jiage2>4.8</td>
    <td><input type=text value="0" name=num2 onkeyup="jisuan();"></td>
    <td><input type="checkbox" name=n2 onclick="jisuan();"></td>
  </tr>
  <tr>
  <td colspan="2">总价:<input type="text" name="jieguo" size="10" value="0"></td>
  </tr>
</table>