how bond dropdownlist gridview edititemtemplate field?

here's formula gridview organization during runtime:

...
<asp:templatefield>
    <edititemtemplate>
        <asp:dropdownlist runat="server" id="ddgvopp" />
    </edititemtemplate>
    <itemtemplate>
        <%# eval("opponent.name") %>
    </itemtemplate>
</asp:templatefield>
...

i wish bond dropdownlist "ddgvopp" nonetheless i don't know how. i should, nonetheless i don't. here's i have, nonetheless i keep removing an "object reference" error, creates sense:

protected vacant gvresults_rowdatabound(object sender, gridviewroweventargs e)
{
    (e.row.rowtype == datacontrolrowtype.datarow) //skip header row
    {
        dropdownlist ddopp = (dropdownlist)e.row.cells[5].findcontrol("ddgvopp");
        bindopponentdd(ddopp);
    }
}

where bindopponentdd() only where dropdownlist gets populated. am i doing right event? not, i need put in?

thanks many advance...