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