求这样一个例子

一个下拉列表，效果是 默认是 折起来的 
               
                                      AAA     点击AAA和BBB或者鼠标放上去后  AAA
                                      BBB                                   aa
                                                                            bb
                                                                            cc
                                                                            BBB
                                                                            dd
                                                                            ee
                                                                            ff 
aa,bb,cc,dd,ee,ff都是在后台动态添加的，我在网上找了好几个列子都是静态的，我 AAA和BBB里面都放的Repeater来获取,但是运行后总是点不出添加的值来（aa,bb,cc,dd,ee,ff），现在快崩溃了，请哪位高手做个这样的例子的提供一下，谢谢了