add the template column in the gridview source along with other columns. take care about the column indexes.
<asp:gridview id="GridView1" runat="server">
<columns>
<asp:templatecolumn headertext="Balance">
<itemtemplate>
<asp:label id="lblBalance" runat="server" text="" />
</itemtemplate>
</asp:templatecolumn>
</columns>
</asp:gridview>
check my updated answer for template column in Solution 2.