传值问题

有一页面A.aspx，一页面B.aspx  其中B.aspx中有一treeview和textbox B.aspx作为被弹出的窗体 如何将B.aspx上的treeview的节点内容显示在textbox中并且将值传回A.aspx我的代码如下：A.aspx:
function ShowOpenWindow(Url,Flag)
    {
    vReturnValue = window.showModalDialog(Url,'11','dialogHeight:330px;dialogWidth:500px;center:1;resizable:0;status:0;scroll:1;help:0;');
    if(typeof(vReturnValue)!="undefined")
    {
    SpvReturnValue=vReturnValue.split("$")
    {
    if(Flag=="Area")
    {
    //document.SearchForm.ClassName.value=SpvReturnValue[0];
    document.getElementById.className.value=SpvReturnValue[0];
    document.SearchForm.ClassRange.value=SpvReturnValue[1];
    }
    else
    {
    document.SearchForm.GroupName.value=SpvReturnValue[0];
    document.SearchForm.DistributeTypeID.value=SpvReturnValue[1];
    }
    }
    }
    }<asp:Button Text="选择" runat="server"  ID="Submit3"/>
<input name="Submit3" type="button" class="Button" onClick="ShowOpenWindow('SelectArea.aspx','Area')" value="选择" id="Button3">
后台代码：this.Label1.Text = Request.QueryString["TitleShow"].ToString();
            flag = Request.QueryString["flag"].ToString();
这两句是page_load里面的   TitleShow,flag这两个变量是从left.aspx框架页面中传值过来的B.aspx代码：<table width="494" border="0" cellspacing="0" cellpadding="0">
        <form id="ClassSelect" name="ClassSelect" method="post" action="" runat="server">  
            <tr><td height="24" align="center" class="Caption">选择区域</td>
            </tr>
              <tr>
                <td height="218" valign="top">
            <div style="height:218px;border:0px inset;overflow:auto;padding:1px;">
                    &nbsp;<asp:TreeView ID="TreeView1" runat="server" OnSelectedNodeChanged="tv_SelectedNodeChanged">
                    </asp:TreeView>
                </div>
            </td>
              </tr>
            <tr>
            <td height="24" class="tableButtom"><table width="100%" border="0" cellspacing="0" cellpadding="0">
              <tr>
                <td height="1" colspan="3" align="right" bgcolor="#666666"></td>
              </tr>
          <tr>
                <td width="16%" height="24" align="right">组名称:</td>
                <td width="66%" align="left"><asp:TextBox ID="ClassName" runat="server"  size="50"></asp:TextBox></td>
                <td width="18%" align="left"><asp:Button ID="aa" runat="server" Text="确定" OnClick="aa_Click"></asp:Button>
                    <input id="Button1" type="button" value="button" onclick="aaaaa()"/>
</td>
              </tr>
            </table></td>
          </tr>
        </form>
        
</table>
后台代码：SqlConnection conn = sqldataserver.GetConnectionInfo();
    DataSet ds;
protected void Page_Load(object sender, EventArgs e)
    {
       conn.Open();
        this.createDataSet();
        conn.Close();
        TreeView1.Nodes.Clear();
        this.InitTree(TreeView1.Nodes, "0");
    }
    private DataSet createDataSet()//返回数据库表
    {
        ds = new DataSet();
        
        string sqlStr = "select * from Class ";
        SqlDataAdapter cmdSelect = new SqlDataAdapter(sqlStr, conn);
        cmdSelect.Fill(ds, "Class");
        return ds;
    }
    protected void InitTree(TreeNodeCollection Nds, string parentId)//用递归方法动态生成节点
    {
        
        DataView dv = new DataView();
        TreeNode tmpNode;
        dv.Table = ds.Tables["Class"];
        dv.RowFilter = "UpID=" + "'" + parentId + "'";
        foreach (DataRowView drv in dv)
        {
            
            tmpNode = new TreeNode();
            tmpNode.Value = drv["ClassID"].ToString();
            tmpNode.Text = drv["ClassName"].ToString();
            //tmpNode.NavigateUrl = "#";//设置超链接
            //tmpNode.SelectAction = TreeNodeSelectAction.None;//禁用超链接属性
            tmpNode.ExpandAll();//展开所有子节点
            Nds.Add(tmpNode);
            this.InitTree(tmpNode.ChildNodes, tmpNode.Value);
        }
        
       
    }
    protected void tv_SelectedNodeChanged(object sender, EventArgs e)
    {
        ClassName.Text = TreeView1.SelectedNode.Text;
    }