Code
<input id="txtTRLastIndex" type="hidden" value="1" />

<table style="width: 428px;" id="SignFrame">
    <tr>
        <td colspan="1" rowspan="2"  >
            </td>
        <td colspan="1" rowspan="2">
        </td>
        <td colspan="1" rowspan="2">
        </td>
    </tr>
   
</table>

Code
<script language="javascript" type="text/javascript">

function Button1_onclick() {
    var signFrame=document.getElementById('SignFrame');
    var a=window.showModalDialog('SelectGoods.aspx');
    
    AddSignRow(a);
    signFrame.bgColor='AliceBlue';
}

function findObj(theObj, theDoc){  var p, i, foundObj;    if(!theDoc) theDoc = document;  if( (p = theObj.indexOf("?")) > 0 && parent.frames.length)  {    theDoc = parent.frames[theObj.substring(p+1)].document;    theObj = theObj.substring(0,p);  }  if(!(foundObj = theDoc[theObj]) && theDoc.all) foundObj = theDoc.all[theObj];  for (i=0; !foundObj && i < theDoc.forms.length; i++)     foundObj = theDoc.forms[i][theObj];  for(i=0; !foundObj && theDoc.layers && i < theDoc.layers.length; i++)     foundObj = findObj(theObj,theDoc.layers[i].document);  if(!foundObj && document.getElementById) foundObj = document.getElementById(theObj);    return foundObj;}
//添加一个参与人填写行
function AddSignRow(a){ //读取最后一行的行号，存放在txtTRLastIndex文本框中 
 var txtTRLastIndex = findObj("txtTRLastIndex",document);
 var rowID = parseInt(txtTRLastIndex.value);
 
 var signFrame = findObj("SignFrame",document);

 //添加行
 var newTR = signFrame.insertRow(signFrame.rows.length);
 newTR.id = "SignItem" + rowID;

 
 //添加列:物品名称
 var newNameTD=newTR.insertCell(0);
 //添加列内容
 newNameTD.innerHTML = "<input name='txtName" + rowID + "' id='txtName" + rowID + "' type='text' size='15'value='"+a+"' />";
 //添加列:数量
 var newEmailTD=newTR.insertCell(1);
 //添加列内容
 newEmailTD.innerHTML = "<input name='txt" + rowID + "' id='txtEmail" + rowID + "' type='text' size='10' />";

 
 //添加列:删除按钮
 var newDeleteTD=newTR.insertCell(2);
 //添加列内容
 newDeleteTD.innerHTML = "<div align='center' style='width:40px'><a href='javascript:;' onclick=\"DeleteSignRow('SignItem" + rowID + "')\">删除</a></div>";
 
 //将行号推进下一行
 txtTRLastIndex.value = (rowID + 1).toString() ;
}

//删除指定行
function DeleteSignRow(rowid){
 var signFrame = findObj("SignFrame",document);
 var signItem = findObj(rowid,document);
 
 //获取将要删除的行的Index
 var rowIndex = signItem.rowIndex;
 
 //删除指定Index的行
 signFrame.deleteRow(rowIndex);
 
 var rowscount = signFrame.rows.length;
 if(rowscount<2) 
    signFrame.bgColor='white';

 
}
//清空列表
function ClearAllSign(){
 if(confirm('确定要清空所有物品吗？')){
  var signFrame = findObj("SignFrame",document);
  var rowscount = signFrame.rows.length;
  
  //循环删除行,从最后一行往前删除
  for(i=rowscount - 1;i > 0; i--){
   signFrame.deleteRow(i);
  }
  
  //重置最后行号为1
  var txtTRLastIndex = findObj("txtTRLastIndex",document);
  txtTRLastIndex.value = "1";
  
  //预添加一行
 }
}


</script>