Coolite的ToggleGroup怎么在后台获取啊。。。

Question

<ext:ImageButton ID="ImageButton1" runat="server" ToggleGroup="G1" ImageUrl="gif/23.gif"
                                                    OverImageUrl="gif/03.gif" DisabledImageUrl="disabled.gif" PressedImageUrl="gif/43.gif" />
                                                
<ext:ImageButton ID="ImageButton2" runat="server" ToggleGroup="G1" ImageUrl="gif/24.gif"
                                                    OverImageUrl="gif/04.gif" DisabledImageUrl="disabled.gif" PressedImageUrl="gif/44.gif" />
                                                
<ext:ImageButton ID="ImageButton3" runat="server" ToggleGroup="G1" ImageUrl="gif/25.gif"
                                                    OverImageUrl="gif/05.gif" DisabledImageUrl="disabled.gif" PressedImageUrl="gif/45.gif" />怎么在后台获取G1里面点的是哪个呢？