如何用Javascript操作gridview中的控件

datagrid如下：
asp:GridView ID="gvDep" runat="server" AutoGenerateColumns="False" OnRowCancelingEdit="gvDep_RowCancelingEdit" OnRowDataBound="gvDep_RowDataBound" OnRowDeleting="gvDep_RowDeleting" OnRowEditing="gvDep_RowEditing" DataKeyNames="DepID">
            <Columns>
                <asp:TemplateField HeaderText="序号">
                    <EditItemTemplate>
                        &nbsp;<asp:Label ID="lbEID" runat="server" Width="30px" Text="<%# Container.DataItemIndex+1 %>"></asp:Label>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="lbID" runat="server" Text="<%# Container.DataItemIndex+1 %>"></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="上级部门">
                    <EditItemTemplate>
                        <asp:TextBox ID="txtFatherDepName" runat="server" Width="93px" Text='<%# Bind("FatherDepName") %>' ReadOnly="True"></asp:TextBox>
                        <asp:Button ID="btnChoise" runat="server"  Text="选择"  />
                        <br />
                        <asp:HiddenField ID="HiddenField1" runat="server" Value='<%# Bind("FatherDepName") %>' />
                      
                    </EditItemTemplate>
                    <ItemTemplate>
                        &nbsp;<asp:Label ID="lbFatherDepName" runat="server" Width="124px"  Text='<%# Bind("FatherDepName") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:CommandField ShowEditButton="True" />
                <asp:CommandField ShowDeleteButton="True" />
            </Columns>
        </asp:GridView>
现需要用javascript操作TextBox ID="txtFatherDepName"，那位知道，请指教，谢谢