datagrid 如何取javascript值

Question

<asp:datagrid id="DataGrid1" runat="server" Width="632px" AutoGenerateColumns="False" OnItemDataBound="DataGrid1_ItemDataBound">
                                                                             <SelectedItemStyle HorizontalAlign="Center"></SelectedItemStyle>
                                                                             <EditItemStyle HorizontalAlign="Center"></EditItemStyle>
                                                                             <AlternatingItemStyle HorizontalAlign="Center"></AlternatingItemStyle>
                                                                             <ItemStyle HorizontalAlign="Center"></ItemStyle>
                                                                             <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                                                                             <FooterStyle HorizontalAlign="Center" VerticalAlign="Middle"></FooterStyle>
                                                                             <Columns>
                                                                                    <asp:TemplateColumn Visible="False" HeaderText="序号">
                                                                                           <ItemTemplate>
                                                                                                  <asp:Label id="car_id" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "car_id") %>' >
                                                                                                  </asp:Label>
                                                                                           </ItemTemplate>
                                                                                    </asp:TemplateColumn>
                                                                                    <asp:BoundColumn DataField="car_code" HeaderText="代码"></asp:BoundColumn>
                                                                                    <asp:TemplateColumn HeaderText="时间">
                                                                                           <ItemTemplate>
                                                                                                  <asp:TextBox id="stime" runat="server" Width="138px" CssClass="TxCss" Text='<%# DataBinder.Eval(Container.DataItem, "car_time") %>'></asp:TextBox>
                                                                                                  
                                                                                                         <IMG id="Image_blqx1" style="WIDTH: 23px; CURSOR: hand; HEIGHT: 15px" onclick="popUpCalendar(this,document.forms[0].stime,'yyyy-mm-dd')"
                                                                                                                src="Celend/Images/calendar.gif">
                                                                                           </ItemTemplate>
                                                                                    </asp:TemplateColumn>
                                                                                    <asp:TemplateColumn HeaderText="地点">
                                                                                           <ItemTemplate>
                                                                                                  <asp:TextBox id=car_place runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "car_place") %>'>
                                                                                                  </asp:TextBox>
                                                                                           </ItemTemplate>
                                                                                           <EditItemTemplate>
                                                                                           </EditItemTemplate>
                                                                                    </asp:TemplateColumn>
                                                                                    <asp:BoundColumn DataField="car_fine" HeaderText="罚款"></asp:BoundColumn>
                                                                                    <asp:BoundColumn DataField="car_points" HeaderText="扣分"></asp:BoundColumn>
                                                                                    <asp:BoundColumn DataField="car_money" HeaderText="代办费"></asp:BoundColumn>
                                                                                    <asp:TemplateColumn HeaderText="操作"></asp:TemplateColumn>
                                                                             </Columns>
                                                                             <PagerStyle VerticalAlign="Middle" HorizontalAlign="Center"></PagerStyle>
                                                                      </asp:datagrid>红色那段代码是真对变量不变的情况下！但是datagrid里的textbox是不一样的！！要怎么取值！把这个事件给他呢？？
popUpCalendar(this,document.forms[0].stime,'yyyy-mm-dd') 这个怎么动态取值呢