<script language="javascript">
function selectNum(n){
var s="<table>";
var num=n;
  for (var i=1;i<num;i++){
 s+='<tr><td width="133" height="28" class="a_lefttd" style="text-align:center"><input name="g'+(i)+'" type="text" id="g'+(i)+'"  style="width:120px" /></td><td width="109"  class="a_lefttd" style=" text-align:center"><select name="c'+(i)+'" id="c'+(i)+'"  style="width:85px; color:#999999"><option value="千足银">千足银</option> <option value="足银">足银</option> <option value="S925">S925</option><option value="其它">其它</option> </select></td><td width="81" class="a_lefttd" style="text-align:center"><select name="u'+(i)+'" id="u'+(i)+'" style="width:60px; color:#999999"> <option value="克">克</option> <option value="件">件</option></select> </td><td width="72" class="a_lefttd" style="text-align:center"><input name="n'+(i)+'" type="text" id="n'+(i)+'" size="5" /></td> <td width="82" class="a_lefttd" style="text-align:center"><input name="p'+(i)+'" type="text" id="p'+(i)+'" size="5" /></td> <td width="76" class="a_lefttd" style=" text-align:center"><input name="j'+(i)+'" type="text" id="j'+(i)+'" size="8" value='+(i)+' /></td> <td width="82" style="text-align:center; border-bottom:#CCCCCC solid 1px"><select name="l'+(i)+'" id="l'+(i)+'" style="color:#999999"> <option value="销售">销售</option> <option value="换新">换新</option> </select></td> </tr>';
} 
s+="</table>"
document.getElementById("spotlst").innerHTML=s; 
}
</script>

<select name="select4" onChange="selectNum(this.value)">
            <option value="1">1</option>
            <option value="2">2</option>
            <option value="3">3</option>
            <option value="4">4</option>
            <option value="5">5</option>
            <option value="6">6</option>
            <option value="7">7</option>
            <option value="8">8</option>
            <option value="9">9</option>
            <option value="10">10</option>
          </select> 

var num = parseInt(n) + 1; //传进来的是字符串，强制转换为整数才行