ASP.net change color of ASP.net GridView template textbox when value changed

Hi

I have 30 template textbox columns in an ASP.net GridView, some of which are shown in the code below. If any text is changed
in these textboxes I want to change the background color of the textbox . What VB.net code would I use to do this?

Thanks

     <asp:TemplateField HeaderText="D1" Visible="false">
                           <ItemTemplate>
                                <asp:Textbox ID="D1" runat="server"  Visible="true" Width="20"></asp:Textbox>
                           </ItemTemplate>
                      </asp:TemplateField>
                      <asp:TemplateField HeaderText="D2" Visible="false">
                           <ItemTemplate>
                                <asp:Textbox ID="D2" runat="server"  Visible="true" Width="20" ></asp:Textbox>
                           </ItemTemplate>
                      </asp:TemplateField>
                     <asp:TemplateField HeaderText="D3" Visible="false">
                           <ItemTemplate>
                                <asp:Textbox ID="D3" runat="server"  Visible="true" Width="20" ></asp:Textbox>
                           </ItemTemplate>
                      </asp:TemplateField>

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