my remarks the cursor moves well in other columns except for one column remarks where the cursor does not move to the next row in the cell.

please help

<script type="text/javascript">
    function enter(obj) {
        var tr = obj.parentNode.parentNode.parentNode;
        var cellIndex = obj.parentNode.cellIndex;
        var rowIndex = obj.parentNode.parentNode.rowIndex;
        if (event.keyCode == 37) //Left
        {
            if (cellIndex > 0)
                tr.parentNode.rows[rowIndex].cells[cellIndex - 1].getElementsByTagName('INPUT')[0].focus();
            return;
        }
        if (event.keyCode == 38) //Up
        {
            if (rowIndex > 1)
                tr.parentNode.rows[rowIndex - 1].cells[cellIndex].getElementsByTagName('INPUT')[0].focus();
            return;
        }
        if (event.keyCode == 39) //Right
        {
            if (cellIndex < tr.cells.length - 1)
                tr.parentNode.rows[rowIndex].cells[cellIndex + 1].getElementsByTagName('INPUT')[0].focus();
            return;
        }
        if (event.keyCode == 40) //Down
        {
            if (rowIndex < tr.parentNode.rows.length - 1)
                tr.parentNode.rows[rowIndex + 1].cells[cellIndex].getElementsByTagName('INPUT')[0].focus();
            return;
        }
    }
</script>

<asp:GridView ID="StudentGridMarks" runat="server" BackColor="White" AutoGenerateColumns="False" AllowPaging="True" OnPageIndexChanging="OnPageIndexChanging" PageSize="45">
    <Columns>
         <asp:TemplateField>
             <HeaderTemplate>
                 <asp:CheckBox ID = "chkAll" runat="server" AutoPostBack="true"  />
             </HeaderTemplate>
             <ItemTemplate>
                 <asp:CheckBox ID="CheckBox1" runat="server" AutoPostBack="true" Enabled="False"  />
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Admno">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox1" runat="server" Text='<%# Eval("admno") %>'></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label1" runat="server" Text='<%# Bind("admno") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="admno" runat="server" Height="16px" Text='<%# Eval("admno") %>' onkeyup="enter(this)" Width="70px"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Names">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("Name") %>' onkeyup="enter(this)" ></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label2" runat="server" Text='<%# Bind("Name") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="Names" runat="server" Height="16px" Text='<%# Eval("Name") %>' onkeyup="enter(this)" Width="245px"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Class">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("Class") %>' ></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label3" runat="server" Text='<%# Bind("Class") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="Classr" runat="server" Height="16px" Text='<%# Eval("Class") %>' onkeyup="enter(this)" Width="34px"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Stream">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox4" runat="server" Text='<%# Bind("Stream") %>'></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label4" runat="server" Text='<%# Bind("Stream") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="Stream" runat="server" Height="16px" Text='<%# Eval("Stream") %>' onkeyup="enter(this)" Width="47px"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Score">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox5" runat="server" Text='<%# Bind("score") %>'></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label5" runat="server" Text='<%# Bind("score") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="Score" runat="server" Height="16px" Text='<%# Eval("score") %>' Width="30px" onkeyup="enter(this)" OnTextChanged="Score_TextChanged"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Agg">
             <EditItemTemplate>
                 <asp:TextBox ID="TxtAgg" runat="server" Text='<%# Bind("Grade") %>' onkeyup="enter(this)" ></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label6" runat="server" Text='<%# Bind("Grade") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="Agg" runat="server" Height="16px" Text='<%# Eval("Grade") %>' onkeyup="enter(this)" Width="28px" Enabled="False"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Remarks">
             <EditItemTemplate>
                 <asp:TextBox ID="txtRemarks" runat="server" Text='<%# Bind("Remark") %>'></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label7" runat="server" Text='<%# Bind("Remark") %>' Visible="False"></asp:Label>
                 <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                     <ContentTemplate>
                         <asp:TextBox ID="Remarks" runat="server" Height="16px" OnTextChanged="Remarks_TextChanged" Text='<%# Eval("Remark") %>' onkeyup="enter(this)" Width="392px"></asp:TextBox>
                     </ContentTemplate>
                 </asp:UpdatePanel>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="UserName">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox8" runat="server" Text='<%# Bind("username") %>'></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label8" runat="server" Text='<%# Bind("username") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="Username" runat="server" Height="16px" Text='<%# Eval("username") %>' onkeyup="enter(this)" Width="89px"></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="DateTime">
             <EditItemTemplate>
                 <asp:TextBox ID="TextBox9" runat="server" Text='<%# Bind("time") %>'></asp:TextBox>
             </EditItemTemplate>
             <ItemTemplate>
                 <asp:Label ID="Label9" runat="server" Text='<%# Bind("time") %>' Visible="False"></asp:Label>
                 <asp:TextBox ID="DateTime" runat="server" Text='<%# Eval("time") %>'></asp:TextBox>
             </ItemTemplate>
         </asp:TemplateField>
    </Columns>
</asp:GridView>