Error:Could not find control 'txtboxname' in ControlParameter 'Name'.

controlID value is taken from code behind.

You can try this:

<asp:controlparameter controlid="boxvalue" name="Name" type="String"  />

<tr>
                       <td>
                           <asp:label id="labelname" runat="server" text="Name:"></asp:label>
                       </td>
                       <td>

                           <asp:textbox id="txtboxname" runat="server" maxlength="20" text="<%# Bind("Name") %>" ></asp:textbox>
                       </td>
<asp:hiddenfield runat="server" id="boxvalue"  />
                   </tr>

and in the code side, wherever the binding of the txtboxname takes place, paste this code:

boxvalue.Value = txtboxname.Text

i.e. assign the hiddenfield id the value of the textbox