asp.net 中的AJAX应用中UpPanel的使用问题

在使用ajax做页面时，碰到了一个问题。
页面使用的dev的PageControl控件，pagecontrol中多个tab每个TAB中有一个下拉框和一个gridview。需求是当下拉框改变时，同时修改gridview中的数据，但是不能影响其他tab中的数据。
实际情况是：变动下拉框时，跟踪代码的执行顺序，是把每个tab中的gridview都进行了更新。
请问，这该如何修改？
aspx代码：           <dxtc:ASPxPageControl ID="ASPxPageControl3" runat="server" ActiveTabIndex="0" 
               Width="100%" OnActiveTabChanged="ASPxPageControl9_ActiveTabChanged" 
               CssClass="list">
               <ActiveTabStyle BackColor="White">
                   <Border BorderColor="#FF9900" BorderStyle="Solid" BorderWidth="2px" />
               </ActiveTabStyle>
               <TabPages>
                   <dxtc:TabPage Text="月报(水源水)">
                       <TabStyle Font-Bold="True" Font-Names="宋体" Font-Overline="False" 
                           Font-Size="10pt" Font-Strikeout="False">
                       </TabStyle>
                       <ContentCollection>
                           <dxw:ContentControl ID="ContentControl3" runat="server">
                               
                               <asp:UpdatePanel ID="up_WaterSource_Month" runat="server">
                                   <ContentTemplate>
                                        <dxe:ASPxLabel ID="lb_WaterSource_Month" runat="server" Text="ASPxLabel">
                                                       </dxe:ASPxLabel>
                                                                                                         <dxe:ASPxComboBox ID="cmb_WaterSource_Month" runat="server" 
                                                           ValueType="System.String" AutoPostBack="True" 
                                                           onselectedindexchanged="cmb_WaterSource_Month_SelectedIndexChanged" 
                                                           Width="80px">
                                                       </dxe:ASPxComboBox>
                                               <dxwgv:ASPxGridView ID="gv_WaterSource_Month" runat="server" 
                                               AutoGenerateColumns="False" Width="100%" 
                                               OnHtmlRowCreated="gv_WaterSource_Month_HtmlRowCreated" CssClass="list">
                                               <Columns>
                                                   <dxwgv:GridViewDataTextColumn Caption="一月" FieldName="M01" Name="M01" 
                                                       VisibleIndex="0" ReadOnly="true">
                                                       <DataItemTemplate>
                                                           <asp:Label ID="lb_M01" runat="server" Text="" />
                                                       </DataItemTemplate>
                                                       <HeaderStyle BackColor="#F1F4BB" HorizontalAlign="center" />
                                                   </dxwgv:GridViewDataTextColumn>
                                                   (省略后面的11列)
                                                   </Columns>
                                           </dxwgv:ASPxGridView>
                                           
                                                                      </ContentTemplate>
                               </asp:UpdatePanel>
                               
                           </dxw:ContentControl>
                       </ContentCollection>
                   </dxtc:TabPage>
                                  </TabPages>
               <Paddings Padding="0px" />
               <TabStyle BackColor="#F1F4BB">
                   <Border BorderWidth="1px" BorderColor="#CACACA" BorderStyle="Solid" />
               </TabStyle>
           </dxtc:ASPxPageControl>
      
CS代码：
代码过长，所以只贴了一个tab中的程序，其他tab类似protected void gv_WaterSource_Month_Init()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("M01");
        dt.Columns.Add("M02");
        dt.Columns.Add("M03");
        dt.Columns.Add("M04");
        dt.Columns.Add("M05");
        dt.Columns.Add("M06");
        dt.Columns.Add("M07");
        dt.Columns.Add("M08");
        dt.Columns.Add("M09");
        dt.Columns.Add("M10");
        dt.Columns.Add("M11");
        dt.Columns.Add("M12");
        dt.Rows.Add("0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0");
        gv_WaterSource_Month.DataSource = dt;
        gv_WaterSource_Month.DataBind();
    }
//中间省略了HtmlRowCreated事件
protected void cmb_WaterSource_Month_SelectedIndexChanged(object sender, EventArgs e)
    {
        lb_WaterSource_Month.Text = "当前年度： " + cmb_WaterSource_Month.Text + " 年";
        gv_WaterSource_Month_Init();
    }