AspxGridView里的Templates里的DetailsView里的一个button单击如果去获取另一个兄弟控件?

布局如下图：

单击“新增地区价格”按钮会操控同级的那个浅绿色的gridview(在DetailsView)里。

            <Templates>
                <DetailRow>
                    <div style="overflow:hidden;line-height:23px;margin-bottom:5px;">
                        <span style="float:left;"><%# Eval("Name") %>地区价格表:</span>
                        <dx:ASPxButton ID="btnExpressAreaAdd" runat="server" Text="新增地区价格" OnClick="btnExpressAreaAdd_Click" style="float:right;">
                            <Paddings Padding="0" />
                        </dx:ASPxButton>    
                    </div>
                    <dx:ASPxGridView ID="agvExpressArea" runat="server" SkinID="agvDetailSkin" Width="100%" OnBeforePerformDataSelect="agvExpressArea_BeforePerformDataSelect">
                        <Columns>
                            <dx:GridViewDataTextColumn Caption="运达地区" FieldName="Area" VisibleIndex="0"></dx:GridViewDataTextColumn>
                            <dx:GridViewDataTextColumn Caption="首重价格(元)" FieldName="FirstCost" VisibleIndex="1"></dx:GridViewDataTextColumn>
                            <dx:GridViewDataTextColumn Caption="续重价格(元)" FieldName="NextCost" VisibleIndex="2">
                            </dx:GridViewDataTextColumn>
                            <dx:GridViewDataTextColumn Caption="类型" FieldName="ItemType" VisibleIndex="3">
                            </dx:GridViewDataTextColumn>            
                            <dx:GridViewCommandColumn Caption="操作" HeaderStyle-HorizontalAlign="Center" Width="60" VisibleIndex="4">
                                <DeleteButton Text="删除" Visible="true" />
                            </dx:GridViewCommandColumn>                
                        </Columns>
                    </dx:ASPxGridView>
                </DetailRow>
            </Templates>